Method and apparatus for illuminating a surface using a projection imaging apparatus

ABSTRACT

A method and illumination optical system forms a modified illumination configuration on an optical integrator so that a secondary light source having a desired modified illumination configuration is formed and light loss is minimized. A light beam shape changing element that diffuses illumination in a plurality of directions, and an angular light beam forming element that forms a plurality of light source images operate together to create a modified illumination configuration on the optical integrator. Since the secondary light source has a desired modified illumination configuration, an aperture stop used to restrict the size and/or shape of the secondary light source blocks only a small amount of illumination, or can be eliminated altogether. It is possible to alter the annular ratio and outer diameter of an annular or quadrupole modified illumination configuration by changing the magnification of a zoom optical system positioned between the light beam shape changing element and the angular light beam forming element. Furthermore, by changing the focal length of a zoom optical system (which is positioned upstream of the optical integrator), it is possible to change the outer diameter of the annular or quadrupole secondary light source without changing the annular ratio thereof.

INCORPORATION BY REFERENCE

[0001] The disclosures of the following priority applications are hereinincorporated by reference: Japanese Patent Application No. 11-90735,filed Mar. 31, 1999; Japanese Patent Application No. 11-284213, filedOct. 5, 1999; Japanese Patent Application No. 11-308186, filed Oct. 29,1999; Japanese Patent Application No. 10-358749, filed Dec. 17, 1998;and Japanese Patent Application No. 11-255636, filed Sep. 9, 1999.

BACKGROUND OF THE INVENTION

[0002] 1. Field of Invention

[0003] The invention relates to a method and apparatus for illuminatinga surface, such as a mask or reticle surface, using a projection imagingapparatus. The invention relates to a method and apparatus fortransferring a pattern, particularly a microdevice (e.g., semiconductordevice (IC, LSI, VLSI), liquid crystal display, thin film magnetic head,image pick-up devices (CCD), etc.) pattern, onto a work (e.g., a wafer,substrate, etc.) and relates to a method for manufacturing themicrodevice.

[0004] 2. Description of Related Art

[0005] In a typical exposure apparatus, light beams emitted from a lightsource are incident on a fly-eye lens and form a secondary light sourcethat includes a plurality of light source images at the focal surface onthe back side of the fly-eye lens. Light beams from the secondary lightsource are restricted by an aperture stop positioned adjacent the backside focal surface of the fly-eye lens, and are then incident on acondenser lens. The aperture stop restricts the shape or size of thesecondary light source to a desired shape or size in accordance with thedesired illumination conditions (exposure conditions).

[0006] The light beams condensed by the condenser lens overlappinglyilluminate a mask that has a prescribed pattern. Light that passesthrough the pattern in the mask forms an image on a wafer via aprojection optical system. In this manner, the mask pattern is projectedand exposed on the wafer. The pattern formed in the mask is highlyintegrated, and in order to accurately copy this detailed pattern ontothe wafer, it is vital that a uniform illumination intensity be obtainedon the wafer.

[0007] In recent years, improvements in illumination performance havebeen obtained by enabling variation of the size of the secondary lightsource formed by the fly-eye lens and changing the coherency τ(τ=aperture stop diameter/illumination optical system pupil diameter, orτ=illumination optical system exit side numerical aperture/illuminationoptical system incident side numerical aperture) of the illumination bychanging the size of the aperture (light transmissive region) of theaperture stop positioned on the exit side of the fly-eye lens. Inaddition, the shape of the secondary light source formed by the fly-eyelens has been restricted into an annular shape or quadrupole shape,which results in improvements in the focal depth and resolving power ofthe projection optical system.

[0008] In order to accomplish modified illumination (annular modifiedillumination or quadrupole modified illumination) by restricting theshape of the secondary light source to an annular shape or a quadrupoleshape, the light beams from the relatively large secondary light sourceformed by the fly-eye lens are restricted by an aperture-stop having anannular shape or quadrupole shape aperture. In other words, with annularmodified illumination or quadrupole modified illumination inconventional technology, the appropriate portions of the light beamsfrom the secondary light source are blocked by the aperture stop, and donot contribute to illumination (exposure). As a result, the illuminationbrightness on the mask and the wafer declines due to the loss of lightin the aperture stop, and the throughput as an exposure apparatus alsodeclines.

[0009] In consideration of the foregoing, it is an objective of thepresent invention to provide an illumination optical apparatus which canaccomplish modified illumination such as annular illumination orquadrupole illumination while satisfactorily suppressing light loss inthe aperture stop.

SUMMARY OF THE INVENTION

[0010] The invention provides an illumination method and apparatus tochange the type and parameters of modified illumination and to obtain afocus depth and resolution for the projection optical system suitablefor the detailed patterns to be exposed and projected. As a result, itis possible to accomplish satisfactory projection exposure with highthroughput under high exposure brightness and satisfactory exposureconditions. In addition, with an exposure method that exposes thepattern on a mask positioned at the target illumination surface onto aphotosensitive substrate using the illumination optical apparatus of thepresent invention, it is possible to accomplish projection exposureunder satisfactory exposure conditions, thereby making it possible toproduce satisfactory devices.

[0011] In one aspect of the invention, an illumination optical systemincludes a light beam shape changing element that diffuses illuminationin a plurality of directions, and an angular light beam forming elementthat forms a plurality of light source images. Together, the light beamshape changing element and the angular light beam forming element createa modified illumination configuration, such as an annular or quadrupoleillumination configuration, on an optical integrator. Thus, the opticalintegrator forms a secondary light source having a desired modifiedillumination configuration. Since the secondary light source has adesired configuration, an aperture stop used to restrict the size and/orshape of the secondary light source blocks only a small amount ofillumination, or can be eliminated altogether.

[0012] The light beam shape changing element can be arranged upstream ofthe angular light beam forming element, or the angular light beamforming element can be arranged upstream of the light beam shapechanging element. The light beam shape changing element can be any typeof optical device that diffuses received light in a plurality ofdirections. For example, the light beam shape changing element can be adiffractive optical element or prism that forms a ring-shaped ormulti-pole-shaped illumination pattern in the far field using incidentparallel light. The angular light beam forming element can be anyoptical device that forms a plurality of light sources from incidentlight, and can be, for example, a fly eye lens or micro fly's eye lens.

[0013] In addition, with the present invention it is possible to alterthe annular ratio and outer diameter of an annular or quadrupolesecondary light source by changing the magnification of a zoom opticalsystem positioned between the light beam shape changing element and theangular light beam forming element. Furthermore, by changing the focallength of a zoom optical system (which is positioned upstream of theoptical integrator), it is possible to change the outer diameter of theannular or quadrupole secondary light source without changing theannular ratio thereof. As a result, it is possible to alter only theannular ratio of the annular or quadrupole secondary light sourcewithout changing the outer diameter thereof by appropriately changingthe focal length of the zoom lens and the magnification of the zoomoptical system.

[0014] The light beam shape changing element and the angular light beamforming element can be made interchangeable with other light beam shapechanging elements and/or the angular light beam forming elements orother optical elements to allow the illumination optical system tocreate a variety of different types of modified illuminationconfigurations or conventional illumination. For example, in oneembodiment, the angular light beam forming element can be replaced withan annular ratio variable optical system that receives light from alight beam shape changing element and varies an annular ratio of anannular illumination configuration formed by the light beam shapechanging element.

[0015] These and other aspects of the invention will be apparent and/orobvious from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention is described in conjunction with the followingdrawings in which like reference numerals refer to like elements, andwherein:

[0017]FIG. 1 is a schematic diagram of an illumination optical apparatusaccording to a first embodiment of the invention;

[0018]FIG. 2 is a schematic diagram of lens elements in an example microfly's eye lens;

[0019] FIGS. 3(a)-3(c) show how a first diffractive optical elementoperates to diffuse received light;

[0020] FIGS. 4(a) and (b) show how an annular illumination configurationis formed by superimposing a plurality of ring-shaped images;

[0021]FIG. 5 shows an annular illumination configuration formed from aplurality of ring-shaped images;

[0022]FIG. 6 is a schematic diagram of an aperture stop turret platehaving a plurality of aperture stop configurations;

[0023] FIGS. 7(a) and (b) shows how an annular ratio and diameter of anannular illumination configuration can be changed;

[0024]FIG. 8 shows an example arrangement of lens elements in a microfly's eye lens;

[0025] FIGS. 9(a)-9(c) show how a second diffractive optical elementoperates to diffuse received light;

[0026]FIG. 10 shows a quadrupolar illumination configuration formed bysuperimposing a plurality of spot images;

[0027]FIG. 11 shows how a quadrupolar illumination configuration can beadjusted in size and shape;

[0028]FIG. 12 is a schematic diagram of an illumination opticalapparatus according to a second embodiment of the invention;

[0029] FIGS. 13(a)-(b) schematically shows the illumination opticalapparatus from a conical prism to the incident surface of the firstfly-eye lens;

[0030] FIGS. 14(a)-(c) schematically show the illumination opticalapparatus from the first fly-eye lens to the aperture stop, and show astate in which light beams obliquely incident on the incident surface ofthe first fly-eye lens form an annular illumination field at theincident surface of the second fly-eye lens;

[0031]FIG. 15 schematically shows the illumination optical apparatusfrom a conical prism to a second fly-eye lens, and the relationshipbetween the magnification of a first zoom lens and the focal length of asecond zoom lens, and the size and shape of the annular illuminationfield formed at the incident surface of the second fly-eye lens;

[0032] FIGS. 16(a)-(c) show a quadrupole secondary light source formedat the back side focal plane of the second fly-eye lens and a quadrupoleaperture stop positioned adjacent thereto;

[0033]FIG. 17 is a schematic diagram of an illumination opticalapparatus according to a third embodiment of the invention;

[0034] FIGS. 18(a) and (b) show how a first exemplary diffractiveoptical element diffuses received light;

[0035] FIGS. 19(a) and (b) show how a second exemplary diffractiveoptical element diffuses received light;

[0036] FIGS. 20(a) and (b) schematically show the illumination opticalapparatus according to the third embodiment, with FIG. 10(b) showing astate in which the magnification of the first zoom lens 5 expanded morethan in the state shown in FIG. 10(a);

[0037]FIG. 21 is a schematic diagram of an illumination opticalapparatus according to a variation of the third embodiment of theinvention;

[0038]FIG. 22 is a schematic diagram of an illumination opticalapparatus according to a fourth embodiment of the invention;

[0039]FIG. 23 is a schematic diagram of an illumination opticalapparatus according to a fifth embodiment of the invention;

[0040]FIGS. 24A and 24B respectively show input and output sides of anexemplary micro fly's eye lens used in the fifth embodiment;

[0041]FIGS. 25A and 25B respectively show exemplary arrangements for themicro fly's eye lens used in the fifth embodiment;

[0042]FIGS. 26A and 26B show first and second quad prism sets includedin the mircolens array;

[0043] FIGS. 27A-C and 28A-B show exemplary illumination configurationsformed on the optical integrator of the fifth embodiment;

[0044]FIG. 29 is a schematic diagram of an illumination opticalapparatus according to a sixth embodiment of the invention;

[0045]FIG. 30A shows a revolver with an exemplary set of interchangeableoptical elements used with the sixth embodiment;

[0046]FIG. 30B shows a revolver with an exemplary set of interchangeableaperture stops used with the sixth embodiment;

[0047] FIGS. 31A-C schematically show an exemplary arrangement for adiffractive optical element used with the sixth embodiment and anillumination configuration intensity profile formed by the diffractiveoptical element;

[0048] FIGS. 32A-C schematically show how a diffractive optical elementused with the sixth embodiment diffuses received light;

[0049]FIGS. 33 and 34A-C show exemplary modified illuminationconfigurations formed on the optical integrator in the sixth embodiment;

[0050]FIGS. 35A and 35B show the relationship between the effectiveregion of the diffractive optical device and the element lenses of theoptical integrator in the sixth embodiment;

[0051]FIGS. 36A and 36B show exemplary modified illuminationconfigurations with four regions on the incident surface in the opticalintegrator;

[0052] FIGS. 37A-37E show exemplary modified illumination configurationshaving multiple regions with edges of the regions continuously inclinedrelative to the scanning direction of the element lenses of the opticalintegrator;

[0053]FIG. 38 shows another exemplary illumination configuration on theincident surface of the optical integrator;

[0054]FIG. 39 schematically shows a protection container for thediffractive optical element in the sixth embodiment;

[0055]FIG. 40 is a schematic diagram of an illumination opticalapparatus according to the seventh embodiment of the invention;

[0056]FIG. 41 is a schematic diagram of a portion of the illuminationoptical apparatus according to an eighth embodiment of the invention;

[0057]FIG. 42 is a schematic diagram of an illumination opticalapparatus according to a ninth embodiment of the invention;

[0058]FIG. 43 is a schematic diagram of an illumination opticalapparatus according to a tenth embodiment of the invention;

[0059]FIG. 44 is a flowchart of steps of a method for forming a patternof an original on a substrate using an imaging device in accordance withthe invention; and

[0060] FIGS. 45A-45D show cross sections of a numerical value example.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0061] First Embodiment

[0062]FIG. 1 is a schematic diagram of an exposure apparatus providedwith the illumination optical apparatus according to a first embodimentof the present invention.

[0063] The exposure apparatus of FIG. 1 includes an excimer laser lightsource 1 that outputs light having a wavelength of 248 nm or 193 nm,although other light sources and wavelength outputs are possible.Substantially parallel light beams emitted along the Z direction by thelight source 1 have a rectangular cross-section that extends lengthwisealong the X direction, and are incident on a beam expander 2 thatincludes a pair of cylindrical lenses 2 a and 2 b. The cylindricallenses 2 a and 2 b have a negative refractive power and a positiverefractive power, respectively, in the plane of the paper in FIG. 1 (theY-Z plane), and function as plane parallel plates in the planeorthogonal to the plane of the paper and including the optical axis AX(the X-Z plane). Accordingly, light beams incident on the beam expander2 are expanded in the plane of the paper in FIG. 1, and are shaped intolight beams having a predetermined rectangular cross-section.

[0064] The substantially parallel light beams transmitted through thebeam expander 2 are deflected in the Y direction by a folding mirror 3,and are then incident on a micro fly's eye lens 4. The micro fly's eyelens 4 is an optical element comprising a plurality of microlenses 4 ahaving positive refractive powers and regular hexagonal shapes arrangeddensely in the vertical and horizontal directions, as shown in FIGS. 1and 2. In general, the microlens groups of the micro fly's eye lens 4are preferably formed by an etching process on a plane parallel glassplate, for example.

[0065] Each of the microlenses of the micro fly's eye lens 4 is smallerthan the lens elements of a conventional fly-eye lens. In addition, themicro fly's eye lens 4, unlike a conventional fly-eye lens that hasmutually isolated lens elements, are formed so that the microlenses arenot mutually isolated. However, the micro fly's eye lens 4 is the sameas a conventional fly-eye lens in that lens elements having a positiverefractive power are arranged in the vertical and horizontal directions.In order to promote clarity in FIGS. 1 and 2, only a very few of themicrolenses 4 a in the micro fly's eye lens 4 are shown compared to theactual number of microlenses 4 a in the array 4.

[0066] Light beams incident on the micro fly's eye lens 4 aretwo-dimensionally partitioned by the plurality of microlenses 4 a, and alight source image is formed at a back side focal plane of eachmicrolens 4 a, i.e., at a plane downstream of the light source 1. Thelight beams from the plurality of light source images formed at the backside focal plane of each microlens 4 a are diffused light beams eachhaving, in this example, a regular hexagonal cross-section, and areincident on an afocal zoom lens 5. Although the zoom lens 5 ispreferably an afocal zoom lens, a focal zoom lens can be used, ifdesired. The afocal zoom lens 5 is composed so that the magnificationthereof is continuously changeable within a predetermined range whilemaintaining an afocal optical system. Thus, the micro fly's eye lens 4is an angular light beam forming element that converts substantiallyparallel light beams from the light source 1 into a plurality of lightsource images that each emit light beams at various angles with respectto the optical axis AX.

[0067] The micro fly's eye lens 4 is removable from the illuminationoptical path, and can be interchanged with another micro fly's eye lens40, as is discussed in more detail below. The micro fly's eye lens 4 andthe micro fly's eye lens 40 are interchanged by a first driving system22 which operates on the basis of commands from a control system 21. Themagnification of the afocal zoom lens 5 is accomplished by a seconddriving system 23 which also operates on the basis of commands from thecontrol system 21.

[0068] Light beams that pass through the afocal zoom lens 5 are incidenton a diffractive optical element (DOE) 6. That is, diffused light beamsfrom each light source image formed at the back side focal plane of themicro fly's eye lens 4 are condensed onto the diffraction surface of thediffractive optical element 6 while maintaining the regular hexagonalcross-section. Thus, the afocal zoom lens 5 links the back side focalplane of the micro fly's eye lens 4 and the diffraction surface of thediffractive optical element 6 as optical conjugates. Furthermore, thenumerical aperture of the light beams collected to one point on thediffraction surface of the diffractive optical element 6 is dependent onthe magnification of the afocal zoom lens 5.

[0069] In this example, the diffractive optical element 6 includes asuccession of levels or steps in a glass substrate having a pitch on theorder of the wavelength of the exposure light (illumination light), anddiffracts an incident beam to a desired angle. Specifically, thediffractive optical element 6 radially diffuses orthogonally incidentlight beams parallel to the optical axis AX in accordance with apredetermined diffusion angle, as shown in FIG. 3(a). In other words, anarrow light beam orthogonally incident on the diffractive opticalelement 6 along the optical axis AX is diffracted in all directions atequal angles centered about the optical axis AX. As a result, the narrowlight beam orthogonally incident on the diffractive optical element 6 isconverted into a diffused light beam having a ring-shaped cross-section.Thus, the diffractive optical element 6 is a light beam changing elementthat converts narrow incident light beams into ring-shaped light beamsdiffused radially.

[0070] As shown in FIG. 3(b), when a wide parallel light beam isorthogonally incident on the diffractive optical element 6, aring-shaped image (ring-shaped light source image) 32 is formed at thefocal position of a lens 31 positioned behind the diffractive opticalelement 6. That is to say, the diffractive optical element 6 forms aring-shaped light intensity distribution at the far field (or theFraunhofer diffraction zone).

[0071] As shown in FIG. 3(c), when a wide parallel light beam incidenton the diffractive optical element 6 is inclined with respect to theoptical axis AX, the ring-shaped image formed at the focal position ofthe lens 31 is shifted. That is to say, when a wide parallel light beamincident on the diffractive optical element 6 is inclined along apredetermined plane (the plane of the paper in FIG. 3), the center ofthe ring-shaped image 33 that is formed at the focal position of thelens 31 is shifted in a direction opposite the direction of inclinationof the light beam along a predetermined plane without the size of thering-shaped image 33 being changed.

[0072] As described above, the diffused light beams from each lightsource image formed at the back side focal plane of the micro fly's eyelens 4 converge on the diffraction surface of the diffractive opticalelement 6 with the regular hexagonal cross-section maintained. In otherwords, when light beams having a plurality of angular components areincident on the diffractive optical element 6, the incident anglethereof is determined by the regular hexagonal conical light beam range.Accordingly, as shown in FIG. 4(a), light beams incident at a maximumangle corresponding to each ridge line of the regular hexagonal conicallight beam range form ring-shaped images 41-46 (indicated by the solidlines in the diagram), centered about the ring-shaped image 47(indicated by the dotted lines in the diagram) formed by light beamsorthogonally incident on the diffractive optical element 6. In FIG.4(b), the condition with the ring-shaped images 41-47 thus formed at thefocal position of the lens 31 are shown superimposed.

[0073] In actuality, an infinite number of light beams having aplurality of angular components determined by the regular hexagonalconical light beam range are incident on the diffractive optical element6, and consequently, an infinite number of ring-shaped images aresuperimposed at the focal position of the lens 31. Thus, an overallannular image like that shown in FIG. 5 is formed when the micro fly'seye lens 4 and the diffractive optical element 6 are positioned alongthe optical axis AX as shown in FIG. 1.

[0074] The diffractive optical element 6 can also be interchanged with adiffractive optical element 60 and a diffractive optical element 61,which are described in more detail below. The diffractive opticalelement 6, the diffractive optical element 60 and the diffractiveoptical element 61 are interchanged by a third driving system 24, whichoperates on the basis of commands from the control system 21.

[0075] With reference again to FIG. 1, light beams that pass through thediffractive optical element 6 are incident on a zoom lens 7. In thisexample, the zoom lens 7 has the same function as the lens 31 shown inFIG. 3. In addition, the incident surface of a fly-eye lens 8 ispositioned adjacent the back side focal plane of the zoom lens 7.Accordingly, light beams passing through the diffractive optical element6 form an annular illumination field at the back side focal plane of thezoom lens 7 and hence at the incident surface of the fly-eye lens 8. Theouter diameter of this annular illumination field depends on the focallength of the zoom lens 7. Thus, the zoom lens 7 makes the diffractiveoptical element 6 and the incident surface of the fly-eye lens 8effectively have the relationship of a Fourier transform. Changing thefocal length of the zoom lens 7 is accomplished by a fourth drivingsystem 25 which acts on the basis of commands from the control system21.

[0076] The fly-eye lens 8 includes a plurality of lens elements havingpositive refractive powers that are arranged densely in the vertical andhorizontal directions. Each lens element of the fly-eye lens 8 has arectangular cross-section similar to the shape of the illumination fieldto be formed on the mask (and hence, similar to the shape of theexposure region to be formed on the wafer). Additionally, the surface onthe incident side of each lens element of the fly-eye lens 8 has aspherical shape with the convexity facing the incident side, and thesurface on the exit side of each lens element has a spherical shape withthe convexity facing the exit side.

[0077] Accordingly, light beams incident on the fly-eye lens 8 aretwo-dimensionally partitioned by the plurality of lens elements, and areformed into light source images at the back side focal plane of eachlens element on which the light beams are incident. In this way, aplurality of annular light sources (hereafter referred to as “secondarylight sources”) are formed at the back side focal plane of the fly-eyelens 8.

[0078] Light beams from the annular secondary light sources formed atthe back side focal plane of the fly-eye lens 8 are incident on anaperture stop 9. This aperture stop 9 is supported on a turret (notshown in FIG. 1) capable of rotating about a predetermined axis parallelto the optical axis AX.

[0079]FIG. 6 is a diagram schematically showing the composition of theturret on which a plurality of aperture stops are positionedcircumferentially. As shown in FIG. 6, eight aperture stops 401-408having optically transmissive regions indicated by the slanted lines inthe diagram are provided along the circumferential direction on a turretsubstrate 400. The turret substrate 400 can rotate about an axisparallel to the optical axis AX around a center point O. Accordingly, byrotating the turret substrate 400, it is possible to position one of theaperture stops 401-408 in the illumination optical path. Rotation of theturret substrate 400 is accomplished by a fifth driving system 26 whichoperates on the basis of commands from the control system 21.

[0080] In this example, three annular aperture stops 401, 403 and 405 ofdiffering annular ratios are formed in the turret substrate 400. Theannular aperture stop 401 has an annular transmissive region with anannular ratio of r11/r21. The annular aperture stop 403 has an annulartransmissive region with an annular ratio of r12/r22. The annularaperture stop 405 has an annular transmissive region with an annularratio of r13/r21.

[0081] Three quadrupole aperture stops 402, 404 and 406 of differingannular ratios are also formed in the turret substrate 400. Thequadrupole aperture stop 402 has four eccentric circular transmissiveregions within an annular region having an annular ratio of r11/r21. Thequadrupole aperture stop 404 has four eccentric circular transmissiveregions within an annular region having an annular ratio of r12/r22. Thequadrupole aperture stop 406 has four eccentric circular transmissiveregions within an annular region having an annular ratio of r13/r21.

[0082] Two circular aperture stops 407 and 408 of differing size(aperture) are also formed in the turret substrate 400. The circularaperture stop 407 has a circular transmissive region with a size of2*r22, while the circular aperture stop 408 has a circular transmissiveregion with a size of 2*r21.

[0083] By selecting and positioning one annular aperture stop out of thethree annular aperture stops 401, 403 and 405 in the illuminationoptical path, it is possible to form annular light beams having threediffering annular ratios and to accomplish three types of annularmodified illumination of differing annular ratios. In addition, byselecting and positioning one quadrupole aperture stop out of the threequadrupole aperture stops 402, 404 and 406 in the illumination opticalpath, it is possible to accurately form four eccentric light beamshaving three differing annular ratios and to accomplish three types ofquadrupole modified illumination of differing annular ratios.Furthermore, by selecting and positioning one circular aperture stop outof the two circular aperture stops 407 and 408 in the illuminationoptical path, it is possible to accomplish two types of regular circularillumination of differing a values. A multiple pole aperture stop (e.g.,binalpole or octalpole aperture stop) which has multi-eccentriccircular, elliptic, or fan-shaped transmissive regions can also be usedas an aperture stop on the turret substrate 400. The transmissiveregions of the quadrupole aperture stops 402, 404 and 406 are not onlycircular-shaped, but can also be elliptic-shaped, or fan-shaped (e.g.,the shape of quarter circles). It is possible for the variable aperturestop (e.g., iris diaphragm) to be attached to the turret substrate 400instead of the circular aperture stops 407 and 408.

[0084] In FIG. 1, annular secondary light sources are formed at the backside focal plane of the fly-eye lens 8 when the micro fly's eye lens 4and the diffractive optical element 6 are positioned along the opticalaxis AX, and consequently one of the annular aperture stops can beselected from the three annular aperture stops 401, 403 and 405 as theaperture stop 9. However, the composition of the turret shown in FIG. 6is intended to illustrative and not limiting with regard to the type ornumber of aperture stops positioned thereon. In addition, the inventionis not limited to a turret-type aperture stop 9, for it is also possibleto use an aperture stop that has an optically transmissive region thatis changeable in size and shape. Furthermore, in place of the twocircular aperture stops 407 and 408, it is possible to provide an irisaperture stop that has a continuously variable circular aperturediameter.

[0085] Light from the secondary light sources that has passed throughthe aperture stop 9 having an annular aperture (light transmission area)is condensed by a condenser optical system 10 that functions as alight-guiding optical system, and uniformly illuminates a mask 11 in anoverlapping manner. Light beams that have passed through a pattern onthe mask 11 form an image of the mask pattern on a wafer 13 having aphotosensitive substrate via a projection optical system 12. In thismanner, the pattern on the mask 11 is successively exposed onto eachexposure region of the wafer 13 by accomplishing bulk exposure or scanexposure while two-dimensionally drive controlling the wafer 13 in theplane orthogonal to the optical axis AX of the projection optical system12 (the X-Y plane).

[0086] In bulk exposure, the mask 11 pattern is exposed in bulk ontoeach exposure region of the wafer 13 in accordance with the so-calledstep and repeat method. In this case, the shape of the illuminationregion on the wafer 13 is a nearly square rectangle, and thecross-sectional shape of each lens element in the fly-eye lens 8 is alsoa nearly square rectangle.

[0087] On the other hand, in scan exposure, the mask 11 pattern is scanexposed onto each exposure region of the wafer 13 while moving the mask11 and wafer 13 relative to the projection optical system 12 inaccordance with the so-called step and scan method. In this case, theshape of the illumination region on the mask 11 is a rectangle with theratio of the length of the short sides to the length of the long sidesbeing for example 1:3, so the cross-sectional shape of each lens elementof the fly-eye lens 8 has a rectangular shape similar to this.

[0088]FIG. 7 is a drawing that schematically shows the illuminationoptical apparatus from the micro fly's eye lens 4 to the incidentsurface of the fly-eye lens 8, and explains the relationship between themagnification of the afocal zoom lens 5 and the focal length of the zoomlens 7, and the size and shape of the annular illumination field formedon the incident surface of the fly-eye lens 8.

[0089] In FIG. 7, a light beam 70 incident along the optical axis AX onthe center of the microlens 4 a positioned on the optical axis AX of themicro fly's eye lens 4 exits along the optical axis AX. The micro fly'seye lens 4 in this example has microlenses of size “a” (a measurementcorresponding to the diameter of a circle circumscribed around a regularhexagon) and focal length f1. The light beam 70 passes through theafocal zoom lens 5 and is then incident on the diffractive opticalelement 6 along the optical axis AX.

[0090] The diffractive optical element 6 forms a light beam 70 a exitingat an angle Θ with respect to the optical axis AX from the light beam 70orthogonally incident along the optical axis AX. The light beam 70 aexiting at angle Θ from the diffractive optical element 6 reaches theincident surface of the fly-eye lens 8 via the zoom lens 7 having focallength f2. The position of the light beam 70 a on the incident surfaceof the fly-eye lens 8 has a height y from the optical axis AX.

[0091] On the other hand, a light beam 71 incident parallel to theoptical axis AX on the uppermost edge of the microlens 4 a positioned onthe optical axis AX in the micro fly's eye lens 4 exits at an angle twith respect to the optical axis AX. This light beam 71 passes throughthe afocal zoom lens 5 having magnification m, and is then incident onthe diffractive optical element 6 at an angle t′ with respect to theoptical axis AX.

[0092] The light beam 71 which is incident on the diffractive opticalelement 6 at an angle t′ with respect to the optical axis AX isconverted into various light beams including a light beam 71 a exitingat an angle (Θ+t′) with respect to the optical axis AX. The light beam71 a exiting from the diffractive optical element 6 at an angle (Θ+t′)with respect to the optical axis AX reaches a height (y+b) from theoptical axis AX at the incident surface of the fly-eye lens 8.

[0093] Furthermore, a light beam 72 incident parallel to the opticalaxis AX on the lowermost edge of the microlens 4 a positioned on theoptical axis AX in the micro fly's eye lens 4 exits at angle t withrespect to the optical axis AX. This light beam 72 passes through theafocal zoom lens 5, and is then incident on the diffractive opticalelement 6 at an angle t′ with respect to the optical axis AX.

[0094] The light beam 72 which is incident on the diffractive opticalelement 6 at angle t′ with respect to the optical axis AX is convertedinto various light beams including a light beam 72 a exiting at an angle(Θ−t′) with respect to the optical axis AX. The light beam 72 a exitingthe diffractive optical element 6 at an angle (Θ−t′) with respect to theoptical axis AX reaches a height (y−b) from the optical axis AX at theincident surface of the fly-eye lens 8.

[0095] Thus, the range reached at the incident surface of the fly-eyelens 8 by the diffused light beams from the various light source imagesformed near the back side focal plane of the micro fly's eye lens 4 is arange having a width of 2 b centered about the height y from the opticalaxis AX. That is to say, as shown in FIG. 7(b), the annular illuminationfield formed at the incident surface of the fly-eye lens 8, and hencethe annular secondary light sources formed at the back-side focal planeof the fly-eye lens 8, have a central height of y from the optical axisAX and a width of 2 b.

[0096] The exit angle t from the micro fly's eye lens 4 and the incidentangle t′ on the diffractive optical element 6 are expressed by equations(1) and (2) below.

t=a/(2×f1)  (1)

t′=t/m=a/(2×f1×m)  (2)

[0097] In addition, the central height y of the annular secondary lightsources, the maximum height (y+b) and the minimum height (y−b) areexpressed by equations (3) through (5) below.

y=f2×sin Θ  (3)

y+b=f2(sin Θ+sin t′)  (4)

y−b=2(sin Θ−sin t′)  (5)

[0098] Accordingly, the annular ratio A stipulated by the ratio of theinner diameter øi to the outer diameter øo of the annular secondarylight sources is expressed by equation (6) below. $\begin{matrix}\begin{matrix}{A = {{\quad {i/}\quad o} = {2{( {y - b} )/( {2( {y + b} )} )}}}} \\{= {( {{\sin \quad \Theta} - {\sin \quad t^{\prime}}} )/( {{\sin \quad \Theta} + {\sin \quad t^{\prime}}} )}} \\{= {( {{\sin \quad \Theta} - {\sin ( {a/( {2 \times {f1} \times m} )} )}} )/( {{\sin \quad \Theta} + {\sin ( {a/( {2 \times {f1} \times m} )} )}} )}}\end{matrix} & (6)\end{matrix}$

[0099] In addition, the outer diameter øo of the annular secondary lightsources is expressed by equation (7) below. $\begin{matrix}\begin{matrix}{{\quad o} = {{2( {y + b} )} = {2 \times {{f2}( {{\sin \quad \Theta} + {\sin \quad t^{\prime}}} )}}}} \\{= {2 \times {{f2}( {{\sin \quad \Theta} + {\sin ( {a/( {2 \times {f1} \times m} )} )}} )}}}\end{matrix} & (7)\end{matrix}$

[0100] Thus, it can be seen by referring to equations (2) through (6)that when the magnification m of the afocal zoom lens 5 changes, onlythe width 2 b of the annular secondary light sources changes, withoutthe central height y thereof changing. That is to say, by changing themagnification m of the afocal zoom lens 5, it is possible to change boththe size (outer diameter øo) and the shape (annular ratio A) of theannular secondary light sources.

[0101] In addition, it can be seen by referring to equations (3) through(7) that when the focal length f2 of the zoom lens 7 is changed, thecentral height y and width 2b of the annular secondary light sourcechanges without the annular ratio A thereof changing. That is to say, bychanging the focal length 12 of the zoom lens 7, it is possible tochange the outer diameter øo of the annular secondary light sourcewithout changing the annular ratio A thereof.

[0102] From the above, it is possible to change only the annular ratio Aof the annular secondary light source without changing the outerdiameter øo thereof by appropriately changing the magnification m of theafocal zoom lens 5 and the focal length 12 of the zoom lens 7.

[0103] Thus, when a diffractive optical element 6 and micro fly's eyelens 4 for annular modified illumination are employed, it is possible toform an annular secondary light source without substantial light loss onthe basis of light beams from the light source 1, and as a result it ispossible to accomplish annular modified illumination whilesatisfactorily suppressing light loss at the aperture stop 9.

[0104] As discussed above, the micro fly's eye lens 4 is interchangeablewith the micro fly's eye lens 40, and the diffractive optical element 6is interchangeable with the diffractive optical element 60. Together,the micro fly's eye lens 40 and the diffractive optical element 60operate to form a quadrupole modified illumination.

[0105] The micro fly's eye lens 40 includes a plurality of microlenses40 a that are square in shape, have a positive refractive power and arearranged densely in the vertical and horizontal directions, as shown inFIGS. 1 and 8. Accordingly, a plurality of light source images areformed on the back side focal plane of the micro fly's eye lens 40, andlight beams from each light source image are diffused light beams eachhaving a square cross-section that are incident on the afocal zoom lens5. Light beams that pass through the afocal zoom lens 5 are incident onthe diffractive optical element 60. The diffused light beams from eachlight source image formed at the back-side focal plane of the microfly's eye lens 40 converge on the diffraction surface of the diffractiveoptical element 60 while maintaining the square cross-section.

[0106] The diffractive optical element 60 converts narrow light beamsorthogonally incident parallel to the optical axis AX into four lightbeams diffused radially in accordance with a single predetermined exitangle, as shown in FIG. 9(a). In other words, narrow light beamsorthogonally incident along the optical axis AX are diffracted alongfour specific directions at equal angles centered about the optical axisAX, and become four narrow light beams. To be more detailed, narrowlight beams orthogonally incident on the diffractive optical element 60are converted into four light beams, the quadrilateral joining thepoints of the four light beams passing through a plane on the back sideparallel to the diffractive optical element 60 forms a square, and thecenter of that square is positioned at the incident axis of the narrowlight beam to the diffractive optical element 60.

[0107] Accordingly, as shown in FIG. 9(b), when a wide parallel lightbeam is orthogonally incident on the diffractive optical element 60,four point images (point-shaped light source images) 92 are formed atthe focal position of a lens 91 positioned on the back side of thediffractive optical element 60. When the wide parallel light beamincident on the diffractive optical element 60 is inclined with respectto the optical axis AX, the four images formed at the focal position ofthe lens 91 move, as shown in FIG. 9(c). That is to say, when the wideparallel light beam incident on the diffractive optical element 60 isinclined along a specific plane, the four point images 93 formed at thefocal position of the lens 91 move in a direction opposite the directionof inclination of the light beams along the specific plane.

[0108] As discussed above, the diffused light beams from the lightsource images formed at the back side focal plane of the micro fly's eyelens 40 converge on the diffraction plane of the diffractive opticalelement 60 while maintaining a square cross-section. In other words,light beams having a plurality of angular components are incident on thediffractive optical element 60, but the angle of incidence thereof isrestricted by the square conical light beam range. That is to say,because an infinite number of light beams having a plurality of angularcomponents determined by the square conical light beam range areincident on the diffractive optical element 60, an infinite number ofpoint images are superimposed at the focal position of the lens 91, sothat a quadrupole image such as the one shown in FIG. 10, is formedoverall. Accordingly, the light beams that have passed through thediffractive optical element 60 form a quadrupole illumination field atthe back side focal plane of the zoom lens 7, and hence at the incidentsurface of the fly-eye lens 8. As a result, a quadrupole secondary lightsource the same as the illumination field formed at the incident surfaceis also formed at the back side focal plane of the fly-eye lens 8.

[0109] In response to switching from the micro fly's eye lens 4 to themicro fly's eye lens 40 and from the diffractive optical element 6 tothe diffractive optical element 60, a switch is also preferably madefrom the annular aperture stop 9 to an aperture stop 9 a. For example,the aperture stop 9 a is one of the quadrupole aperture stops selectedfrom among of the three quadrupole aperture stops 402, 404 and 406.

[0110] Thus, when the micro fly's eye lens 40 and diffractive opticalelement 60 for quadrupole modified illumination are employed, it ispossible to form a quadrupole secondary light source without substantialloss of light from the light source 1, and as a result is it possible toaccomplish quadrupole modified illumination while satisfactorilysuppressing light loss in the aperture stop 9 a.

[0111] As shown in FIG. 11, it is possible to define the shape and sizeof the quadrupole secondary light source similar to the annularsecondary light source. In this case, the size of each microlens 40 a inthe micro fly's eye lens 40 corresponds to the diameter of a circlecircumscribed around the square that is the cross-sectional shape of themicrolens 40 a. Thus, similar to the case of annular modifiedillumination, by changing the magnification m of the afocal zoom lens 5,it is possible to alter both the annular ratio A and the outer diameterøo of the quadrupole secondary light source. In addition, by changingthe focal length f2 of the zoom lens 7, it is possible to alter theouter diameter øo of the quadrupole secondary light source withoutaltering the annular ratio thereof. As a result, by appropriatelychanging the magnification m of the afocal zoom lens 5 and the focallength f2 of the zoom lens 7, it is possible to alter only the annularratio A of the quadrupole secondary light source without changing theouter diameter øo thereof.

[0112] Next, an explanation will be provided for the case of normalcircular illumination which is obtained by withdrawing both the microfly's eye lenses 4 and 40 from the illumination optical path, andsetting the diffractive optical element 61 for circular illumination inthe illumination optical path in place of the diffractive opticalelements 6 and 60.

[0113] In this case, light beams having a rectangular cross-section areincident on the afocal zoom lens 5 along the optical axis AX. Lightbeams incident on the afocal zoom lens 5 are enlarged or reduced inaccordance with the magnification of the lens, exit from the afocal zoomlens 5 along the optical axis AX as light beams still having a squarecross-section, and are incident on the diffractive optical element 61.

[0114] The diffractive optical element 61 for circular illumination hasthe function of converting the incident square light beams into circularlight beams. Accordingly, the circular light beams formed by thediffractive optical element 61 form a circular illumination fieldcentered about the optical axis AX at the incident surface of thefly-eye lens 8. As a result, a circular secondary light source centeredabout the optical axis AX is also formed at the back side focal plane ofthe fly-eye lens 8. In this case, it is possible to appropriately alterthe outer diameter of the circular secondary light source by changingthe focal length f2 of the zoom lens 7.

[0115] Corresponding to the withdrawal of the micro fly's eye lenses 4and 40 from the illumination optical path and the setting of thediffractive optical element 61 for circular illumination in theillumination optical path, a change from the annular aperture stop 9 orthe quadrupole aperture stop 9 a to the circular aperture stop 9 b isalso preferably made. The circular aperture stop 9 b can be one circularaperture stop selected from among the two circular aperture stops 407and 408, and has an aperture the size of which corresponds to thecircular secondary light source.

[0116] Hereafter, the operation of interchanging illumination in thepresent embodiment will be described in more detail.

[0117] First, information relating to the various types of masks to besuccessively exposed in accordance with the step and repeat method orthe step and scan method is input into the control system 21 via aninput means 20 such as a keyboard. The control system 21 stores in aninternal memory unit information such as the optimum line width(resolution) and focus depth relating to each type of mask, and suppliesappropriate control signals to the first driving system 22 through thefifth driving system 26 in response to input from the input means 20.

[0118] That is to say, when annular modified illumination is required toform an optimum resolution and focus depth, the first driving system 22positions the micro fly's eye lens 4 for annular modified illuminationin the illumination optical path on the basis of commands from thecontrol system 21. In addition, the third driving system 24 positionsthe diffractive optical element 6 for annular modified illumination inthe illumination optical path on the basis of commands from the controlsystem 21. Furthermore, in order to obtain an annular secondary lightsource having the desired size (outer diameter) and annular ratio at theback side focal plane of the fly-eye lens 8, the second driving system23 sets the magnification of the afocal zoom lens 5 on the basis ofcommands from the control system 21, and the fourth driving system 25sets the focal length of the zoom lens 7 on the basis of commands fromthe control system 21. Additionally, in order to restrict the annularsecondary light source while satisfactorily suppressing light loss, thefifth driving system 26 rotates the turret on the basis of commands fromthe control system 21 and positions the desired annular aperture stop inthe illumination optical path.

[0119] In this manner, it is possible to form an annular secondary lightsource without substantial loss of light beams from the light source 1,and as a result it is possible to accomplish annular modifiedillumination without substantial light loss in the aperture stop 9.

[0120] Furthermore, it is possible to appropriately adjust, asnecessary, the size and annular ratio of the annular secondary lightsource formed at the back side focal plane of the fly-eye lens 8 bychanging the magnification of the afocal zoom lens 5 using the seconddriving system 23 and changing the focal length of the zoom lens 7 usingthe fourth driving system 25. In this case, the turret is rotated inaccordance with changes in the size and annular ratio of the annularsecondary light source, and the annular aperture stop 401, 403, 405having the desired size and annular ratio is selected and positioned inthe illumination optical path.

[0121] In this manner, it is possible to accomplish various types ofannular modified illumination by appropriately changing the size andannular ratio of the annular secondary light source without substantiallight loss in the formation or restriction of the annular secondarylight source.

[0122] In addition, when quadrupole modified illumination is requiredfor an optimum resolution and focus depth, the first driving system 22positions the micro-fly's eye lens 40 for quadrupole modifiedillumination in the illumination optical path and the third drivingsystem 24 positions the diffractive optical element 60 for quadrupolemodified illumination in the illumination optical path. Furthermore, inorder to obtain a quadrupole secondary light source having the desiredsize (outer diameter) and shape (annular ratio) at the back side focalplane of the fly-eye lens 8, the second driving system 23 sets themagnification of the afocal zoom lens 5 on the basis of commands fromthe control system 21, and the fourth driving system 25 sets the focallength of the zoom lens 7 on the basis of commands from the controlsystem 21. Additionally, in order to restrict the quadrupole secondarylight source while satisfactorily suppressing light loss, the fifthdriving system 26 rotates the turret on the basis of commands from thecontrol system 21 and positions the desired quadrupole aperture stop402, 404, 406 in the illumination optical path.

[0123] In this manner, it is possible to form a quadrupole secondarylight source without substantial light loss on the basis of light beamsfrom the light source 1, and as a result it is possible to accomplishquadrupole modified illumination without substantial light loss in theaperture stop which restricts the light beams from the secondary lightsource.

[0124] Furthermore, it is possible to appropriately adjust, asnecessary, the size and shape of the quadrupole secondary light sourceformed at the back side focal plane of the fly-eye lens 8 by changingthe magnification of the afocal zoom lens 5 using the second drivingsystem 23 and changing the focal length of the zoom lens 7 using thefourth driving system 25. In this case, the turret is rotated inaccordance with changes in the size and shape of the quadrupolesecondary light source, and the quadrupole aperture stop 402, 404, 406having the desired size and shape is selected and positioned in theillumination optical path.

[0125] In this manner, it is possible to accomplish various types ofquadrupole modified illumination by appropriately changing the size andshape of the quadrupole secondary light source without substantial lightloss in the formation or restriction of the quadrupole secondary lightsource.

[0126] Furthermore, when regular circular illumination is required foran optimum resolution and focus depth, similar adjustments to theillumination optical system can be made under the control of the controlsystem 21. In this manner, it is possible to form a circular secondarylight source without substantial loss of light from the light source 1,and as a result it is possible to accomplish regular circularillumination without substantial light loss in the aperture stop whichrestricts the light beams from the secondary light source.

[0127] With the above-described embodiment, it is possible to accomplishregular circular illumination and modified illumination such as annularmodified illumination or quadrupole modified illumination whilesatisfactorily suppressing light loss in the aperture stop used forrestricting the secondary light source. Additionally, it is possible tochange the parameters of modified illumination or regular circularillumination while satisfactorily suppressing light loss in the aperturestop, through the simple operation of changing the magnification of theafocal zoom lens and changing the focal length of the zoom lens.Accordingly, it is possible to appropriately change the type of modifiedillumination and the parameters thereof, and to obtain the resolutionand focal depth of the projection optical system suitable for thedetailed pattern to be exposed and projected. As a result, it ispossible to accomplish satisfactory projection exposure with highthroughput under satisfactory exposure conditions and high exposurebrightness.

[0128] Thus, in an exemplary embodiment of the present invention, anangular light beam forming element and a light beam shape changingelement are positioned on the optical path between the light source andthe optical integrator. Specifically, the angular light beam formingelement includes a diffused light beam forming element such as a microfly's eye lens that converts the substantially parallel light beams fromthe light source means into a plurality of light source images fromwhich light beams diffused at various angles with respect to thestandard optical axis emerge. An optical system such as an afocal zoomlens condenses the diffused light beams formed by the micro fly's eyelens and guides the beams to the diffraction surface of a diffractiveoptical element functioning as the light beam shape changing element.Accordingly, substantially parallel light beams from the light sourcethat pass through the micro fly's eye lens and the afocal zoom lensbecome light beams having a plurality of angular components with respectto the standard optical axis and then are incident on the diffractiveoptical element.

[0129] The light beam shape changing element includes a light beamchanging element such as a diffractive optical element that convertsnarrow incident light beams into a radially diffused ring-shaped lightbeam or plurality of light beams. An optical system such as a zoom lensforms an annular illumination field or plurality of illumination fieldseccentric with respect to the standard optical axis on the incidentsurface of the optical integrator such as a fly-eye lens from thering-shaped light beam or plurality of light beams formed by thediffractive optical element. In general, the plurality of illuminationfields or secondary light sources eccentric with respect to the standardoptical axis means are, for example, bipolar or multipole (tripole,quadrupole octopole or the like) illumination fields or secondary lightsources, but quadrupole illumination fields or secondary light sourceswill be formed for illustrative purposes.

[0130] By thus employing an angular light beam forming element composedof a micro fly's eye lens, and a light beam shape changing elementincluding a diffractive optical element, an annular illumination fieldor quadrupole illumination field can be formed on the incident surfaceof the fly-eye lens. As a result, an annular or quadrupole secondarylight source is similarly formed on the back side focal plane of thefly-eye lens. The light beams from the annular or quadrupole secondarylight source formed by the fly-eye lens in this manner are restricted bythe aperture stop having an aperture corresponding to the size and shapeof the secondary light source and then overlappingly illuminate the maskthat is the target illumination surface.

[0131] The above explanation describes an example wherein semiconductordevices are manufactured using a photolithography process and a waferprocess employing a projection exposure apparatus, but liquid crystaldisplay devices, thin-film magnetic heads and image detectors (e.g.,CCDs and the like) can also be manufactured as semiconductor devices bya photolithography process that uses this exposure apparatus.

[0132] In the above-described embodiment, it is possible to compose thediffractive optical elements that function as light beam changingelements and the micro fly's eye lenses that function as angular lightbeam forming elements so as to be positioned in the illumination opticalpath using a turret method, for example. In addition, it is alsopossible to use a commonly-known slider mechanism to accomplish mountingand removal or interchanging of the above-described micro fly's eyelenses and diffractive optical elements.

[0133] In addition, with the above-described embodiment, the shape ofthe microlenses 4 a comprising the micro fly's eye lens 4 for annularmodified illumination is set to a regular hexagon. A regular hexagon wasselected as a polygon close to a circle because dense arrangement isimpossible with circular microlenses, so light loss is generated. Thisnotwithstanding, the shape of each microlens 4 a in the micro fly's eyelens 4 for annular modified illumination is not limited to this, andother appropriate shapes can be used. Similarly, the shape of themicrolenses 40 a in the micro fly's eye lens 40 for quadrupole modifiedillumination is set to a square, but it is possible to use otherappropriate shapes including a rectangle.

[0134] In addition, with the above-described embodiment, the refractivepower of each microlens comprising the micro fly's eye lens was assumedto be a positive refractive power, but the refractive power of thesemicrolenses may also be negative.

[0135] Furthermore, an afocal zoom lens was employed, but it is alsopossible to employ a focal zoom lens in place of the afocal zoom lens 5or 7 and to position a diffractive optical element for converting squarelight beams into circular light beams in front of the micro fly's eyelens.

[0136] In addition, with the above-described embodiment, a singlefly-eye lens 8 was employed, but it is also possible to apply thepresent invention to a double fly-eye method employing two fly-eyelenses.

[0137] Furthermore, the diffractive optical element 61 was positioned inthe illumination optical path when accomplishing regular circularillumination, but it is also possible to omit use of this diffractiveoptical element 61.

[0138] In addition, it is also possible to use, as necessary, a fly-eyelens or diffractive optical element in place of the micro fly's eye lensas a diffused light beam forming element.

[0139] Furthermore, with the above-described embodiment, a diffractiveoptical element is employed as a light beam changing element, but thisis intended to be illustrative and not limiting. It is also possible toemploy a refractive optical element such as a micro fly's eye lens or amicrolens prism, as shown in the fifth embodiment described below.

[0140] Furthermore, with the above-described embodiment, an aperturestop for restricting the light beams of the secondary light source ispositioned adjacent the back side focal plane of the fly-eye lens 8.However, it is also possible to have an arrangement where the aperturestop is omitted and the light beams from the secondary light source arecompletely unrestricted, e.g., by making the cross-sectional area ofeach lens element comprising the fly-eye lens sufficiently small.

[0141] In addition, with the above-described embodiment, the presentinvention was described using as an example a projection opticalapparatus provided with an illumination optical apparatus, but it isclear that it is possible to apply the present invention to a generalillumination optical apparatus for uniformly illuminating a targetillumination surface other than a mask.

[0142] In the above-described embodiment, light from the secondary lightsource formed at the position of the aperture stop 9 is condensed by thecondenser lens 10 functioning as a light-guiding optical system andoverlappingly illuminates the mask 11, but an illumination fieldaperture stop (mask blind) and a relay optical system for forming animage of this illumination field aperture stop on the mask 11 can bepositioned between the condenser lens 10 and the mask 11. In this case,the light-guiding optical system would include the condenser lens 10 andthe relay optical system, the condenser lens 10 would condense lightfrom the secondary light source formed at the position of the aperturestop 9 and overlappingly illuminate the illumination field aperturestop, and the relay optical system would form an image of the apertureof the illumination field aperture stop on the mask 11.

[0143] In addition, in the above-described embodiment, a fly-eye lens 8which is a wave front dividing (splitting) integrator is employed as anoptical integrator, but if an internal reflection type (Rod-type)integrator (e.g., light pipe, light tunnel, glass rod, etc.) is used asthe optical integrator, the system should be arranged as describedbelow. That is, a condenser optical system should be added on thedownstream side of the zoom lens 7 to form a conjugate surface to thediffractive optical element 6. Furthermore, the rod-type integratorshould be positioned such that the incident edge is positioned adjacentthis conjugate plane. Additionally, a relay optical system is preferablypositioned for forming an image of the illumination field aperture stoppositioned at the exit side surface or adjacent the exit side surface ofthis rod-type integrator on the mask 11. In the case of thisarrangement, the second prescribed plane is the pupil plane of thecomposite system of the zoom lens 7 and the above-described condenseroptical system, and the secondary light source is formed on the pupilplane of the relay optical system (a virtual image of the secondarylight source is formed adjacent the incident side of the rod-typeintegrator). In this case, the relay optical system used for guidinglight beams from the rod-type integrator to the mask 11 becomes thelight-guiding optical system.

[0144] Second Embodiment

[0145]FIG. 12 is a schematic diagram of an illumination optical systemin which a light beam shape changing element is positioned upstream ofan angular light beam forming element. That is, the embodiment shown inFIG. 12 has the relative positions of the light beam shape changingelement and the angular light beam forming element reversed compared tothe embodiment shown in FIG. 1.

[0146] The system shown in FIG. 12 is similar in many respects to thatin FIG. 1, so description of common elements, functions or otherfeatures is not provided.

[0147] Light beams transmitted by the beam expander 2 are deflected inthe Y direction by a folding mirror 3 and are incident on a conicalprism 6. The surface of the conical prism 6 on the mask 11 side (thesurface to the right in the drawing) is formed in a planar shapeorthogonal to the optical axis AX. The surface of the conical prism 6 onthe light source 1 side (the surface to the left in the drawing) has aconical concave surface. More specifically, the refractive surface ofthe conical prism 6 on the light source 1 side corresponds to a surfaceof a cone symmetric with respect to the optical axis AX. Accordingly,light beams incident on the conical prism 6 are deflected along alldirections at the same angle centered about the optical axis AX and arethen incident on the afocal zoom lens 5. In this way, the conical prism6 comprises a light beam shape changing member for diffusing light beamsfrom the light source 1 into substantially annular light beams.

[0148] In FIG. 12, the conical concave surface of the conical prism 6faces the light source 1 side, but the conical prism 6 can be positionedsuch that the conical concave side faces the mask 11 side. In addition,the conical prism 6 is interchangeable with a pyramidal prism 6 a asanother light beam shape changing member. The composition and action ofthis pyramidal prism 6 a will be described below.

[0149] Similar to the embodiment shown in FIG. 1, the afocal zoom lens 5can be adjusted to continuously change the magnification within apredetermined range while maintaining an afocal system.

[0150] Interchanging of the conical prism 6 and pyramidal prism 6 a isperformed by a driving system 22 which operates on the basis of commandsfrom a control system 21. In addition, changing the magnification of theafocal zoom lens 5 is accomplished by a zoom driving system 23 on thebasis of commands from the control system 21.

[0151] Light beams from the prism 6 that are incident on the afocal zoomlens 5 form a ring-shaped light source image at the pupil plane of thelens 5. Light from the ring-shaped light source image formssubstantially parallel light beams and exits from the afocal zoom lens5, to be incident on a first fly-eye lens 4 (an angular light beamforming element) that functions as a first optical integrator. Lightbeams from oblique directions substantially symmetrical with respect tothe optical axis AX are incident on the incident surface of the firstfly-eye lens 4. In other words, light beams are obliquely incident alongall directions at the same angle centered about the optical axis AX.

[0152] The first fly-eye lens 4 includes, for example, of a plurality oflens elements each having a square cross-section and a positiverefractive power, said lens elements arranged in the vertical andhorizontal directions along the optical axis AX. The surface on theincident side of each lens element is formed into a spherical shape withthe convex surface facing the incident side, and the exit side surfacesare formed into a planar shape.

[0153] Accordingly, light beams incident on the first fly-eye lens 4 arepartitioned two-dimensionally by the plurality of lens elements, and onering-shaped light source image is formed at the back side focal plane ofeach lens element. Light beams from the plurality of ring-shaped lightsource images formed at the back side focal plane of the first fly-eyelens 4 pass through a zoom lens 7 and then overlappingly illuminate asecond fly-eye lens 8 which functions as a second optical integrator.The zoom lens 7 is a relay optical system that can continuously changeits focal length within a predetermined range, and links the back sidefocal plane of the first fly-eye lens 4 and the back-side focal plane ofthe second fly-eye lens 8 as substantially optical conjugates. Inaddition, the zoom lens 7 comprises a telecentric optical system on theback side. In order to satisfy the above-described conjugaterelationship and telecentricity, the zoom lens 7 is preferably amulti-group zoom lens with at least three zoom lens groups capable ofindependent movement. Changing the focal length of the zoom lens 7 isaccomplished through a zoom driving system 24 which operates on thebasis of commands from the control system 21.

[0154] Accordingly, at the incident surface of the second fly-eye lens8, an illumination field with a shape in which infinitely manyillumination fields each having a square shape similar to thecross-sectional shape of each lens element of the first fly-eye lens 4are arranged at positions equidistant from the optical axis AX, that isto say an annular illumination field centered about the optical axis AX,is formed.

[0155] The second fly-eye lens 8 includes a plurality of lens elements,each having a positive refractive power, arranged in the vertical andhorizontal directions along the optical axis AX, the same as the firstfly-eye lens 4. However, each lens element comprising the second fly-eyelens 8 has a rectangular cross-section similar to the shape of theillumination field to be formed on the mask (and hence, the shape of theexposure region to be formed on the wafer). In addition, the surface onthe incident side of each lens element in the second fly-eye lens 8 isformed in a spherical shape or an aspherical shape with the convexsurface facing the incident side, and the surface on the exit side isformed in a spherical shape or an aspherical shape with the convexsurface facing the exit side.

[0156] Accordingly, light beams incident on the second fly-eye lens 8are partitioned two-dimensionally by the plurality of lens elements, anda plurality of light source images are respectively formed at the backside focal plane of each lens element on which the light beams areincident. In this way, a plural light source (hereafter referred to asthe “secondary light source”) of the same annular shape as theillumination field formed by the light beams incident on the secondfly-eye lens 8 is formed at the back side focal plane of the secondfly-eye lens 8.

[0157] Light beams from the annular secondary light source formed at theback side focal plane of the second fly-eye lens 8 are incident on anaperture stop 9. This aperture stop 9 is supported on a turret capableof rotating about a predetermined axis parallel to the optical axis AX.The turret can be constructed the same as or similar to the turretdescribed above and shown in FIG. 6.

[0158] In FIG. 12, annular secondary light sources are formed at theback side focal plane of the second fly-eye lens 8, and consequently oneof the annular aperture stops is preferably selected from the threeannular aperture stops 401, 403 and 405 as the aperture stop 9. However,the composition of the turret shown in FIG. 6 is intended toillustrative and not limiting with regard to the type or number ofaperture stops positioned thereon or even the use of a rotating turretfor the aperture stop 9.

[0159] Light from the secondary light sources that passes through theaperture stop 9 having an annular aperture (light transmission area) iscondensed by a condenser optical system 10, and then uniformlyilluminates a mask 11 in an overlapping manner. Light beams that passthrough the pattern on the mask 11 form an image of the mask 11 patternon a wafer 13 via the projection optical system 12.

[0160]FIG. 13 schematically shows the illumination optical system fromthe conical prism 6 to the incident surface of the first fly-eye lens 4.

[0161] As shown in FIG. 13(a), light beams deflected by the conicalprism 6 along all directions at the same angle α centered about theoptical axis AX pass through the afocal zoom lens 5 having amagnification ml and are then obliquely incident on the incident surfaceof the first fly-eye lens 4 along all directions at the same angle Θ1centered about the optical axis AX. The size of the illumination fieldformed at the incident surface of the first fly-eye lens 4 is dl.

[0162] As shown in FIG. 13(b), when the magnification of the afocal zoomlens 5 is changed from m1 to m2, light beams deflected by the conicalprism 6 along all directions at the same angle α centered about theoptical axis AX pass through the afocal zoom lens 5 having amagnification m2 and are then obliquely incident on the incident surfaceof the first fly-eye lens 4 along all directions at the same angle Θ2centered about the optical axis AX. At this time, the size of theillumination field formed at the incident surface of the first fly-eyelens 4 is d2.

[0163] The relationships shown by equations (8) and (9) below hold forthe angles of incidence Θ1 and Θ2 of the light beams on the incidentsurface of the first fly-eye lens 4, the sizes d1 and d2 of theillumination fields formed at the incident surface of the first fly-eyelens 4, and the magnifications m1 and m2 of the afocal zoom lens 5.

Θ2=(m1/m2)×Θ1  (8)

d2=(m2/m1)×d1  (9)

[0164] With reference to equation (8), it can be seen that it ispossible to continuously change the incident angle Θ of the light beamson the incident surface of the first fly-eye lens 4 by continuouslychanging the magnification m of the afocal zoom lens 5.

[0165]FIG. 14 schematically shows the illumination optical system fromthe first fly-eye lens 4 to the aperture stop 9.

[0166] In FIG. 14(a), light beams incident at a predetermined angle froma predetermined direction onto the incident surface of the first fly-eyelens 4 pass through each lens element and are then obliquely incident onthe zoom lens 7 while-maintaining the same angle. Thus, an illuminationfield having a predetermined width at a position eccentric to theoptical axis AX by a predetermined distance is formed on the incidentsurface of the second fly-eye lens 8, as indicated by the solid lines inthe drawing.

[0167] In actuality, light beams are incident on the incident surface ofthe first fly-eye lens 4 from oblique directions substantiallysymmetrical about the optical axis AX, as shown by the dashed lines inthe drawing. In other words, light beams are incident along alldirections at the same angle centered about the optical axis AX.Accordingly, at the incident surface of the second fly-eye lens 8, anannular illumination field centered about the optical axis AX is formed,as shown in FIG. 14(b). In addition, an annular secondary light sourcethe same as the illumination field formed at the incident surface isalso formed at the back side focal plane of the second fly-eye lens 8.On the other hand, as discussed above, an annular aperture (the portionin white in FIG. 14(c)) corresponding to the annular secondary lightsource is formed in the annular aperture stop 9 positioned adjacent theback side focal plane of the second fly-eye lens 8.

[0168] In this manner, when the conical prism 6 is employed as the lightbeam shape changing element, it is possible to form an annular secondarylight source with substantially no light loss, and as a result it ispossible to accomplish annular modified illumination without substantiallight loss at the aperture stop 9.

[0169]FIG. 15 schematically shows the illumination optical system fromthe conical prism 6 to the incident surface of the second fly-eye lens8, and is used to explain the relationship between the magnification ofthe afocal zoom lens 5 and the focal length of the zoom lens 7, and thesize and shape of the annular illumination field formed at the incidentsurface of the second fly-eye lens 8.

[0170] In FIG. 15, the central light ray of the light beam exiting fromthe conical prism 6 at an angle α centered about the optical axis AXpasses through the afocal zoom lens 5 having a magnification of m, andis then incident on the first fly-eye lens 4 at an angle Θ from theoptical axis. The first fly-eye lens 4 includes lens elements each ofsize “a” and focal length f1. The central light ray exiting at an angleΘ from a lens element of the first fly-eye lens 4 arrives at the secondfly-eye lens 8 via the zoom lens 7 which has a focal length fr. At thistime, the incident range of the light beam at the incident surface ofthe second fly-eye lens 8 is a range having a width b centered about aheight y from the optical axis AX. That is to say, the illuminationfield formed at the incident surface of the second fly-eye lens 8, andhence the secondary light source formed at the back side focal plane ofthe second fly-eye lens 8, has a width b and a height y from the opticalaxis, as shown in FIG. 14(b).

[0171] The exit angle α from the conical prism 6 and the incident angleΘ on the first fly-eye lens 4 have the relationship shown in thefollowing equation (10).

Θ=(1/m)×α  (10)

[0172] In addition, the height y and width b of the annular secondarylight source are respectively expressed by equations (11) and (12)below.

y=fr×sin Θ  (11)

b=(fr/f1)×α  (12)

[0173] Accordingly, the annular ratio A stipulated by the ratio of theinner diameter øi to the outer diameter øo of the annular secondarylight source is expressed by equation (13) below.

A=øi/øo=(2y−b)/(2y+b)={2f1×sin(α/m)−a}/{2f1×sin(α/m)+a}  (13)

[0174] In addition, the outer diameter øo of the annular secondary lightsource is expressed by equation (14) below.

øo=2y+b=fr{2 sin(α/m)+a/f1}  (14)

[0175] Changing the form of equation (14), the relationship shown inequation (15) can be obtained.

fr=øo/{2 sin(α/m)+a/f1}  (15)

[0176] Thus, with reference to equations (10) and (11), it can be seenthat when only the magnification m of the afocal zoom lens 5 changeswith no change in the focal length fr of the zoom lens 7, the height yof the annular secondary light source changes with no change in thewidth b thereof. That is to say, by changing only the magnification m ofthe afocal zoom lens 5, it is possible to change both the size (outerdiameter øo) and the shape (annular ratio A) of the annular secondarylight source without changing the width b thereof.

[0177] In addition, with reference to equations (11) and (12), it can beseen that when only the focal length fr of the zoom lens 7 is changedwith no change in the magnification m of the afocal zoom lens 5, boththe width b and height y of the annular secondary light source change inproportion to the focal length fr. That is to say, by changing only thefocal length fr of the zoom lens 7, it is possible to change the size(outer diameter øo) of the annular secondary light source withoutchanging the shape (annular ratio A) thereof.

[0178] Furthermore, with reference to equations (13) and (15), it can beseen that by changing the magnification m of the afocal zoom lens 5 andthe focal length fr of the zoom lens 7 so as to satisfy the relationshipin equation (15) for an outer diameter øo of a certain size, it ispossible change only the shape (annular ratio A) of the annularsecondary light source without changing the size (outer diameter øo)thereof.

[0179] An explanation is now provided below for changes in themagnification m of the afocal zoom lens 5 and the focal length fr of thezoom lens 7 for a case wherein the shape (annular ratio A) of theannular secondary light source is changed without changing the size(outer diameter øo) thereof in accordance with a specific numericalexample.

[0180] In this first numerical example, the deflection angle α by theconical prism 6 is taken to be 7 degrees, the size “a” of each lenselement of the first fly-eye lens 4 is taken to be 2.5 mm and the focallength f1 of each lens element is taken to be 50 mm. Furthermore, withthe outer diameter øo of the annular secondary light source set to 96 mmand kept constant, the magnification m of the afocal zoom lens 5 and thefocal length fr of the zoom lens 7 needed in order to change the annularratio A of the annular secondary light source from around 0.24 to around0.95 are respectively found. Table (1) below shows the correspondingrelationships between the magnification m of the afocal zoom lens 5, theannular ratio A of the annular secondary light source, and the focallength fr of the zoom lens 7 in the first numerical example. TABLE 1 m Afr 0.1 0.94817 49.75678 0.2 0.916468 80.19026 0.3 0.881258 113.9927 0.40.846487 147.3723 0.5 0.812679 179.8279 0.6 0.779947 211.2513 0.70.748299 241.6332 0.8 0.717711 270.9975 0.9 0.688146 299.3801 1.00.659561 326.8211 1.1 0.631915 353.3616 1.2 0.605165 379.0419 1.30.57927 403.901 1.4 0.554191 427.9763 1.5 0.529893 451.3031 1.6 0.506338473.9151 1.7 0.483496 495.8439 1.8 0.461334 517.1198 1.9 0.439822537.7711 2.0 0.418933 557.8247 2.1 0.39864 577.3059 2.2 0.378918596.2387 2.3 0.359744 614.6459 2.4 0.341095 632.549 2.5 0.32295 649.96822.6 0.305289 666.9228 2.7 0.288092 683.4313 2.8 0.271343 699.5108 2.90.255023 715.1778 3.0 0.239117 730.448

[0181] With reference to Table 1, it can be seen that in order to changethe annular ratio A from around 0.5 to around 0.69, it is only necessaryto change the magnification m of the afocal zoom lens 5 from around 1.6to around 0.9 and change the focal length fr of the zoom lens 7 fromaround 474 mm to around 300 mm.

[0182] As discussed above, the conical prism 6 is interchangeable withthe pyramidal prism 6 a. An explanation is now provided for the casewhere the pyramidal prism 6 a is set in the illumination optical pathinstead of the conical prism 6.

[0183] With the pyramidal prism 6 a, the mask-side surface has a planarshape orthogonal to the optical axis AX. In addition, thelight-source-side surface has four refractive surfaces and is formedwith an overall pyramidal concavity facing the light source 1. The fourrefractive surfaces correspond to the pyramidal surfaces (the sidesurfaces without the bottom surface) of a square pyramid having fourridge lines along the X axis and the Z axis with one point on theoptical axis AX as the vertex. That is to say, the four refractivesurfaces correspond to the pyramidal surfaces of a square pyramidsymmetric about the optical axis AX. Similar to the case of the conicalprism 6, the pyramidal prism 6 a may also be positioned so that thepyramidal concavity faces the mask 11.

[0184] When the pyramidal prism 6 a is positioned in the illuminationoptical path, light beams incident on the pyramidal prism 6 a aredeflected along four predetermined directions at equal angles centeredabout the optical axis AX and are incident on the afocal zoom lens 5. Inthis way, the pyramidal prism 6 a comprises a light beam shape changingelement that changes the light beams from the light source 1 into fourlight beams eccentric to the optical axis AX. The light beams incidenton the afocal zoom lens 5 form four point-shaped light source images onthe pupil plane of the lens 5. In this case, the quadrilateral joiningthe four point-shaped light source images forms a square with sidesparallel to the X axis and the Z axis and centered about the opticalaxis AX. Light from these four point-shaped light source images exitsthe afocal zoom lens 5 as substantially parallel light beams and is theincident on the first fly-eye lens 4. Here, light beams from obliquedirections substantially symmetrical with respect to the optical axis AXare incident on the incident surface of the first fly-eye lens 4. To bemore specific, the light beams are oblique along four specificdirections at equal angles, centered about the optical axis AX.

[0185] Accordingly, four point-shaped light source images arerespectively formed at the back-side focal plane of each lens element ofthe first fly-eye lens 4. Light beams from the plurality of point-shapedlight source images formed at the back side focal plane of the firstfly-eye lens 4 pass through a zoom lens 7 and then overlappinglyilluminate the second fly-eye lens 8. Accordingly, at the incidentsurface of the second fly-eye lens 8, four square illumination fieldssimilar to the cross-sectional shape of each lens element of the firstfly-eye lens 4 made eccentric (parallel shifted) equidistantly outwardlyalong four symmetric radial directions about the optical axis AX areformed. As a result, as shown in FIG. 16(a) a quadrupole secondary lightsource (the portion indicated by the shaded area in FIG. 16(a)) is alsoformed at the back side focal plane of the second fly-eye lens 8.

[0186] In conjunction with the switch from the conical prism 6 to thepyramidal prism 6 a, a switch is also preferably made from the annularaperture stop 9 to aperture stop 9 a. The aperture stop 9 a is onequadrupole aperture stop selected from three quadrupole aperture stops402, 404 and 406. As shown in FIG. 16(b), four circular apertures (theparts indicated by the white regions in FIG. 16(b)) having the size of acircle that can be drawn substantially inside the four square lightsources are formed in the quadrupole aperture stop 9 a. Additionally, asshown in FIG. 16(c) it is also possible to use a quadrupole aperturestop 9 a having four apertures in the shape of quarter circles (theparts indicated by the white regions in FIG. 16(c)).

[0187] In this manner, even when the pyramidal prism 6 a is used as thelight beam shape changing element, it is possible to form a quadrupolesecondary light source without substantial light loss, and as a resultit is possible to accomplish quadrupole modified illumination whilesatisfactorily suppressing light loss in the aperture stop 9 a.

[0188] Furthermore, by changing only the magnification m of the afocalzoom lens 5, it is possible to change the position of the light centerof the four square light sources in the quadrupole secondary lightsource. In other words, it is possible to change the size and shape ofthe quadrupole secondary light source without changing the widththereof. As shown by the dashed lines in FIG. 16(a), it is possible todefine the size and shape of the quadrupole secondary light sourcesimilarly to that of an annular secondary light source. The annularratio of the quadrupole secondary light source can be defined on thebasis of the ratio øi/øo. In this case, the width b of the quadrupolesecondary light source is defined as {fraction (1/2)} the differencebetween the diameter øi of the small circle and the diameter øo of thelarge circle.

[0189] In addition, by changing only the focal length fr of the zoomlens 7, it is possible to change only the size of the quadrupolesecondary light source without changing the shape (annular ratio)thereof. Furthermore, by changing the magnification m of the afocal zoomlens 5 and the focal length fr of the zoom lens 7 so as to satisfy aprescribed relationship, it is possible to change only the shape of thequadrupole secondary light source without changing the size thereof.

[0190] On the other hand, when the conical prism 6 is withdrawn from theillumination optical path, light beams having a square cross-section areincident along the optical axis AX on the afocal zoom lens 5. The lightbeams incident on the afocal zoom lens 5 are reduced or enlarged inaccordance with the magnification of the lens, exit from the afocal zoomlens 5 along the optical axis AX while maintaining a squarecross-section, and are then incident on the first fly-eye lens 4.Accordingly, one point-shaped light source image is formed at the backside focal plane of each lens element of the first fly-eye lens 4. Inaddition, at the incident surface of the second fly-eye lens 8, a squareillumination field similar to the cross-sectional shape of each lenselement of the first fly-eye lens 4 is formed, centered about theoptical axis AX. As a result, a square secondary light source centeredabout the optical axis AX can also be formed at the back side focalplane of the second fly-eye lens 8.

[0191] In conjunction with withdrawing the conical prism 6 from theillumination optical path, the annular aperture stop 9 is preferablyinterchanged with the circular aperture stop 9 b. The circular aperturestop 9 b is selected from the two circular aperture stops 407 and 408,and has an aperture size that can be substantially inscribed in thesquare secondary light source.

[0192] In this way, it is possible to form a square secondary lightsource without substantial light loss, and to accomplish regularcircular illumination while satisfactorily suppressing light loss in theaperture stop.

[0193] In this case, by changing the magnification m of the afocal zoomlens 5 or the focal length fr of the zoom lens 7, it is possible toappropriately change the size of the square secondary light source.

[0194] With the above embodiment, light beam shape changing element ispositioned in the optical path between the light source and an angularlight beam forming element. The light beam shape changing elementconverts light beams from the light source into light beams incident onthe angular light beam forming element from oblique directionssubstantially symmetrical with respect to the standard optical axis.Specifically, the light beam shape changing element can include aconical prism or a pyramidal prism, although it is also possible toemploy a diffractive optical element, as discussed above.

[0195] Light beams the shape of which has been altered by the light beamshape changing element are condensed by a condenser optical system andare overlappingly incident on the angular light beam forming elementfrom oblique directions substantially symmetrical with respect to thestandard optical axis. In this manner, a first plural light source isformed by the angular light beam forming element. Light beams from thefirst plural light source are condensed by a relay optical system andare guided to an optical integrator. As a result, it is possible to forman annular light source or a plurality of light sources eccentric to thestandard optical axis as a second plural light source, that is to say asecondary light source, using the optical integrator.

[0196] Here, when a conical prism is employed as the light beam shapechanging element, an annular light source is formed, and when apyramidal prism is employed, a plurality of light sources eccentric tothe optical axis are formed. In particular, when a four-sided pyramidalprism (hereafter referred to simply as “pyramidal prism”) is employed asthe pyramidal prism, a secondary light source composed of four lightsources symmetrically eccentric to the standard optical axis, that is tosay a quadrupole secondary light source, is formed. In this way, lightbeams from the annular or quadrupole secondary light source formed bythe optical integrator illuminate the target illumination surface afterbeing restricted by an aperture stop preferably having an aperturecorresponding to the size and shape of the secondary light source.Moreover, it is possible to use a multi-sided (e.g., an eight-sided)pyramidal prism as the pyramidal prism.

[0197] In addition, with the present embodiment the condenser opticalsystem can include a zoom optical system of variable magnification, andby changing the magnification of the zoom optical system, it is possibleto alter the annular ratio of the annular light source formed as thesecond plural light source or to alter the position of each light centerof the plurality of light sources formed as the second plural lightsource. Furthermore, if the relay optical system positioned in theoptical path between the angular light beam forming element and theoptical integrator includes a zoom optical system of variablemagnification, it is possible to alter the size of the second plurallight source by changing the zoom ratio of this zoom optical system.

[0198] Third Embodiment

[0199]FIG. 17 schematically shows an illumination optical systemaccording to a third embodiment of the present invention. In addition,FIGS. 18 and 19 are used to explain the action of the diffractiveoptical element in this embodiment. In the drawings relating to theembodiment and variations below (FIG. 17, FIG. 21 and FIG. 22), theinput means 20, the control system 21, the light beam shape changingmember driving system 22, the zoom driving systems 23 and 24 and theturret driving member 25 (which does not exist in FIG. 12) are omitted.

[0200] The third embodiment has a composition similar to that of thesecond embodiment. However, the only fundamental difference is that inthis embodiment diffractive optical elements are employed as light beamshape changing elements. Accordingly, in FIG. 17, elements having thesame function as elements in the first and second embodiments areassigned the same reference numbers as in FIG. 1.

[0201] Light beams that pass through a beam expander 2 are deflected bythe folding mirror 3 and are then incident on a diffractive opticalelement 6 b. The diffractive optical element 6 b in this exampleincludes binary or multiple levels (or steps) having a pitch on theorder of the wavelength of the exposure light (illumination light)formed on a glass substrate, and diffracts the incident beam to adesired angle. Specifically, as shown in FIG. 18(a), a narrow light beamorthogonally incident on the diffractive optical element 6 b along theoptical axis AX is diffracted in all directions at equal angles centeredabout the optical axis AX, and forms a ring-shaped beam. Accordingly,when a parallel beam of square cross-section is incident on thisdiffractive optical element 6 b along the optical axis AX, an annularbeam results, as shown in FIG. 18(b). Thus, the diffractive opticalelement 6 b constitutes a light beam shape changing element thatdiffuses light beams from the light source 1 into annular light beams.

[0202] That is to say, the diffractive optical element 6 b has the sameaction as the conical prism 6 in deflecting beams orthogonally incidentthereon along the optical axis AX into beams in all directions at equalangles centered about the optical axis AX. However, whereas the conicalprism 6 deflects the entirety of the incident light beams in alldirections at equal angles centered about the optical axis AX, thediffractive optical element 6 b deflects each beam comprising theincident light beam in all directions at equal angles centered about theincident axis thereof (parallel to the optical axis AX). Accordingly,the afocal zoom lens 5 is configured so as to link the diffractiveoptical element 6 b and the incident surface of the first fly-eye lens 4as substantially optically conjugate.

[0203] In this way, as in the second embodiment, a ring-shaped lightsource image is formed at the pupil plane of the afocal zoom lens 5.Furthermore, substantially parallel light beams exiting from the afocalzoom lens 5 are obliquely incident on the incident surface of the firstfly-eye lens 4 in all directions at equal angles centered about theoptical axis AX. As a result, an annular secondary light source isformed at the back side focal plane of the second fly-eye lens 8 withoutsubstantial light loss. In addition, light loss for the most part doesnot occur at the aperture stop 9 positioned adjacent the back side focalplane of the second fly-eye lens 8. Furthermore, by appropriatelychanging the magnification m of the afocal zoom lens 5 and the focallength fr of the zoom lens 7, it is possible to change the size andshape (annular ratio) of the annular secondary light source, the same asin the first embodiment.

[0204] In the third embodiment, the diffractive optical element 6 b isinterchangeable with another diffractive optical element 6 c. When thediffractive optical element 6 b is withdrawn from the illuminationoptical path, it is possible to accomplish regular circular illuminationthe same as when the conical prism 6 and pyramidal prism 6 a arewithdrawn in the second embodiment. The case wherein the diffractiveoptical element 6 c instead of the diffractive optical element 6 b isset in the illumination optical path is explained below.

[0205] When the diffractive optical element 6 c is used as the lightbeam shape changing element, narrow beams orthogonally incident alongthe optical axis AX are diffracted along four specific directions atequal angles centered about the optical axis AX, and form four narrowbeams, as shown in FIG. 19(a). Accordingly, when parallel beams with asquare cross-section are incident on this diffractive optical element 6c along the optical axis AX, quadrupole beams result, as shown in FIG.19(b). Thus, the diffractive optical element 6 c constitutes a lightbeam shape changing element that changes light beams from the lightsource 1 into four light beams eccentric to the optical axis AX.Accordingly, four point-shaped light source images are formed at thepupil plane of the afocal zoom lens 5, the same as when the pyramidalprism 6 a is employed in the second embodiment.

[0206] Furthermore, substantially parallel light beams exiting from theafocal zoom lens 5 are then obliquely incident on the incident surfaceof the first fly-eye lens 4 along four specific directions at equalangles centered about the optical axis AX. As a result, a quadrupolesecondary light source is formed at the back side focal plane of thesecond fly-eye lens 8 without substantial light loss. In addition, thisquadrupole secondary light source is restricted while satisfactorilysuppressing light loss by an aperture stop 9 a positioned adjacent theback side focal plane of the second fly-eye lens 8. Furthermore, byappropriately changing the magnification m of the afocal zoom lens 5 andthe focal length fr of the zoom lens 7, it is possible to change thesize and shape of the quadrupole secondary light source.

[0207]FIG. 20 schematically shows a configuration of an illuminationoptical device according to a first variation of the third embodiment.FIG. 20(b) shows a state in which the magnification of the afocal zoomlens 5 is expanded more than the state shown in FIG. 20(a).

[0208] This first variation differs from the third embodiment only inthat a micro fly's eye lens 4 a is employed as the first opticalintegrator (angular light beam forming element).

[0209] In the first variation shown in FIG. 20, a micro fly's eye lens 4is employed instead of the first fly-eye lens 4. The micro fly's eyelens 4 is an optical element that includes a plurality of microlensesarranged in the horizontal and vertical directions, and for example isformed by etching a plane parallel glass plate. Accordingly, eachmicrolens is smaller than each lens element in a typical fly-eye lens,but the element is the same as the fly-eye lens in that lens elementshaving a positive refractive power are arranged in the horizontal andvertical directions. Accordingly, the micro fly's eye lens 4accomplishes the same action as the first fly-eye lens 4.

[0210] Changes in the magnification m of the afocal zoom lens 5 and thefocal length fr of the zoom lens 7 when changing only the shape (annularratio A) of the annular secondary light source without changing the size(outer diameter øo) thereof in the first variation employing thediffractive optical element 6 b and the micro fly's eye lens 6 a are nowexplained below with reference to a specific numerical example.

[0211] In this second numerical example, the diffraction angle(deflection angle) a by the diffractive optical element 6 b is taken tobe 7 degrees, the size “a” of each microlens in the micro fly's eye lens6 a is taken to be 0.5 mm and the focal length f1 of each microlens istaken to be 10 mm. Furthermore, with the outer diameter øo of theannular secondary light source set to 96 mm and kept constant, themagnification m of the afocal zoom lens 5 and the focal length fr of thezoom lens 7 needed in order to change the annular ratio A of the annularsecondary light source from around 0.24 to around 0.95 are respectivelyfound. Table 2 below shows the corresponding relationships among themagnification m of the afocal zoom lens 5, the annular ratio A of theannular secondary light source, and the focal length fr of the zoom lens7 in the second numerical example. TABLE 2 m A fr 0.1 0.94817 49.756780.2 0.916468 80.19026 0.3 0.881258 113.9927 0.4 0.846487 147.3723 0.50.812679 179.8279 0.6 0.779947 211.2513 0.7 0.748299 241.6332 0.80.717711 270.9975 0.9 0.688146 299.3801 1.0 0.659561 326.8211 1.10.631915 353.3616 1.2 0.605165 379.0419 1.3 0.57927 403.901 1.4 0.554191427.9763 1.5 0.529893 451.3031 1.6 0.506338 473.9151 1.7 0.483496495.8439 1.8 0.461334 517.1198 1.9 0.439822 537.7711 2.0 0.418933557.8247 2.1 0.39864 577.3059 2.2 0.378918 596.2387 2.3 0.359744614.6459 2.4 0.341095 632.549 2.5 0.32295 649.9682 2.6 0.305289 666.92282.7 0.288092 683.4313 2.8 0.271343 699.5108 2.9 0.255023 715.1778 3.00.239117 730.448

[0212] Comparing Table 1 and Table 2, it can be seen that thecorresponding relationships among the magnification m of the afocal zoomlens 5, the annular ratio A and the focal length fr of the zoom lens 7match in the first numerical example and the second numerical example.This illustrates that when the micro fly's eye lens 6 a is employedinstead of the first fly-eye lens 4, it is possible to achieve the sameaction numerically as with the first fly-eye lens 4 by appropriatelysetting the size a and focal length f1 of each microlens.

[0213]FIG. 21 schematically shows the composition of an illuminationoptical apparatus according to a second variation of the thirdembodiment.

[0214] This second variation differs from the third embodiment only inthat the afocal zoom lens 5 is removed and the diffractive opticalelement 6 b and the first fly-eye lens 4 are positioned adjacent eachother, and the rest of the composition is the same as that of the thirdembodiment. Accordingly, in FIG. 21, elements having the same functionas elements in the second embodiment are assigned the same referencenumbers as in FIG. 17.

[0215] As discussed above, the afocal zoom lens 5 links the diffractiveoptical element 6 b and first fly-eye lens 4 as optical conjugates, andhas the function of changing the angle of the incident light beams onthe incident surface of the first fly-eye lens 4. Accordingly, even ifthe afocal zoom lens 5 is removed from the illumination optical path andthe diffractive optical element 6 b and the incident surface of thefirst fly-eye lens 4 are positioned adjacent each other, the angle ofthe incident light beams on the incident surface of the first fly-eyelens 4 is determined by the diffraction angle of the diffractive opticalelement 6 b. Accordingly, in the second variation, it is possible tochange the size of the annular secondary light source formed at the backside focal plane of the second fly-eye lens 8 by changing the focallength of the zoom lens 7, but it is not possible to change the annularratio thereof.

[0216] Fourth Embodiment

[0217]FIG. 22 schematically shows the composition of an illuminationoptical apparatus according to a fourth embodiment of the presentinvention.

[0218] The fourth embodiment has a composition similar to that of thesecond embodiment. However, the only fundamental difference is that inthe second embodiment a fly-eye lens is employed as an opticalintegrator, but in this fourth embodiment an internal reflection type(Rod-type) integrator (e.g., light pipe, light tunnel, glass rod, etc.,hereafter referred to simply as a “rod-type integrator”) is employed asthe optical integrator. Accordingly, in FIG. 22, elements having thesame function as elements in the second embodiment are assigned the samereference numbers as in FIG. 12.

[0219] In this embodiment, a rod-type integrator 8 a and a condenserlens 7 a are mounted in the optical path between the zoom lens 7 and animaging optical system 10 a, and the aperture stop for restricting thesecondary light source is removed. Here, the composite optical systemcomposed of the zoom lens 7 and the condenser lens 7 a links the backside focal plane of the first fly-eye lens 4 and the incident surface ofthe rod-type integrator 8 a as substantially optically conjugate. Inaddition, the imaging optical system 10 a links the exit surface of therod-type integrator 8 a and the mask 11 as substantially opticallyconjugate.

[0220] The rod-type optical integrator 8 a is an internalreflection-type glass rod formed of a glass material such as silicaglass or fluorite, and uses total reflection at the boundary surfacebetween the inside and the outside, that is to say at the inner surface,to form light source images, the number of which corresponds to thenumber of internal reflections, along a surface that is parallel to therod incident surface and that passes through the convergence point.Nearly all of the light source images formed are virtual images, withonly the center (i.e., the convergence point) light source image being areal image. That is to say, light beams incident on the rod-typeintegrator 8 a are partitioned in the angular direction by internalreflection, and a secondary light source which is composed of aplurality of light source images is formed along a surface that isparallel to the incident surface of the rod and that passes through theconvergence point. In the case of this fourth embodiment, an annularsecondary light source is formed when the conical prism 6 is employed asthe light beam shape changing element, and a quadrupole secondary lightsource is formed when the pyramidal prism 6 a is used.

[0221] Light beams from the secondary light source formed by therod-type integrator 8 a at the incident side thereof are superimposed atthe exit surface thereof, and then pass through the imaging opticalsystem 10 a and uniformly illuminate the mask 11. As discussed above,the imaging optical system 10 a links the exit surface of the rod-typeintegrator 8 a and the mask 11 (and hence, the wafer 13) assubstantially optically conjugate. Accordingly, a rectangularillumination field similar to the cross-sectional shape of the rod-typeintegrator 8 a is formed on the mask 11.

[0222] In this manner, it is possible, while satisfactorily suppressinglight loss as in the above embodiments, to accomplish annular modifiedillumination by using the conical prism 6 as the light beam shapechanging element, to accomplish quadrupole modified illumination byusing the pyramidal prism 6 a as the light beam shape changing element,and to accomplish regular circular illumination by withdrawing the lightbeam shape changing element from the illumination optical path. Inaddition, by appropriately changing the magnification m of the afocalzoom lens 5 and the focal length fr of the zoom lens 7, it is possibleto change the size and shape of the secondary light source.

[0223] In accomplishing circular aperture illumination in theabove-described embodiments and variations, the light beam shapechanging element is preferably withdrawn from the illumination opticalpath. By withdrawing the light beam shape changing element(6, 6 a, 6 b),it is possible to have the composition of a so-called double fly-eyesystem, as is disclosed in U.S. Pat. No. 4,497,015 (which corresponds toJapanese Unexamined Patent Publication No. Sho 58-147708).

[0224] When doing this, in the apparatus having the compositionillustrated in FIGS. 12, 17 and 22, the afocal zoom lens 5 may bewithdrawn at the same time. In addition, in the apparatus having thecomposition illustrated in FIG. 21, the first fly-eye lens 4 may bewithdrawn at the same time and in its place a different fly-eye lenssuitable for the illumination conditions may be disposed in theillumination optical path as the first fly-eye lens. In addition in thethird embodiment, it is possible to used a diffractive optical elementwhich forms a circular illumination field at a far field to accomplishcircular illumination.

[0225] In addition in the fourth embodiment, the conical or pyramidalprism was employed as the light beam shape changing element, but it isalso possible to employ a diffractive optical element such as in thethird embodiment.

[0226] In addition, in the above-described embodiments and variations, aprism having a conical concave surface was employed as the conicalprism, but it is also possible to employ a prism having a convex conicalsurface. Similarly, for the pyramidal prism, it is possible to employ aprism having convex pyramidal surfaces.

[0227] In addition, in the above-described embodiments and variations,the present invention was explained using as an example a projectionexposure apparatus provided with an illumination optical apparatus, butit is clear that it is also possible to apply the present invention to ageneral illumination optical apparatus for uniformly illuminating atarget illumination surface other than a mask.

[0228] Furthermore, in the above-described embodiments and variations,the light source is a KrF excimer laser that supplies light with awavelength of 248 nm, or an ArF excimer laser that supplies light with awavelength of 193 nm, but naturally the present invention can be appliedto an apparatus provided with a light source other than this. Forexample, it is possible to use as the light source of the presentinvention a laser light source such as an F₂ laser that supplies lightwith a wavelength of 157 nm, or a light source unit or the like composedof the combination of a laser light source that supplies light at aprescribed wavelength and a non-linear optical element that changes thelight from the laser light source into light with a wavelength of 200 nmor less.

[0229] In the second through fourth embodiments, the operation ofinterchanging illumination is similar to the first embodiment. Inaddition, in the third and fourth embodiments, driving systems andcontrol systems are not shown in FIGS. 17 and 21. The illuminationoptical system of the third embodiment has a driving system whichcontrols interchanging the diffractive optical elements 6 b and 6 c, azoom driving system which controls the magnification of the afocal zoomlens 5, a zoom driving system which controls the focal length of thezoom lens 7, and a driving system which controls the aperture stops (theturret substrate 400).

[0230] Fifth Embodiment

[0231]FIG. 23 is a schematic diagram of an illumination opticalapparatus according to a fifth embodiment of the present invention.

[0232] The exposure apparatus of FIG. 23 preferably has either a KrF orArF excimer laser as a light source 601. Nearly parallel light beamsemitted from the light source 601 in the direction of the Y-axis enterthe diffractive optical device 604 through the unit magnification relayoptical system 602. In the unit magnification relay optical system 602,the output side mirror of a pair of (not shown) resonator mirrors in thelight source 601 and the diffractive optical device 604 are made to besubstantially optically conjugate.

[0233] The diffractive optical device 604 transforms and emits theentering light with a rectangular cross-section as a nearly circularcross-section in the far field (Fraunhofer diffraction region). Thelight emitted from the diffractive optical device 604 enters istransmitted by an afocal zoom lens 605 to a special fly-eye lens 606,which is removable relative to the illumination path.

[0234]FIG. 24A is an oblique view of the special fly-eye lens 606 fromthe incident direction of the light, and FIG. 24B is an oblique view ofthe special fly-eye lens 606 from the exit direction of the light. InFIG. 24A and FIG. 24B, the same coordinate system as FIG. 23 isprovided.

[0235] The special fly-eye lens 606 has multiple lens surfaces 606 adensely arranged in a matrix shape as shown in FIG. 24A. The specialfly-eye lens 606 also has multiple prism surfaces 606 b densely arrangedin a matrix shape as shown in FIG. 24B. The multiple prism surfaces 606b each correspond to the multiple lens surfaces 606 a. Here, themultiple lens surfaces 606 a and the multiple prism surfaces 606 b areformed by performing an etching process, for example, on parallel flatglass plates.

[0236]FIG. 25 is a cross section of the special fly-eye lens describedin FIG. 24A and FIG. 24B. Preferably, the fly-eye lens 606 has themultiple lens surface 606 a and the multiple prism surface 606 b on thefront and the back surfaces of one substrate, as described in FIG. 25A,but it may be structured, as described in FIG. 25B, in such a mannerthat the multiple lens surface 631 a is provided on the front surface ofa substrate 631 while the multiple prism surface 632 b is provided onthe back surface of another substrate 632. In this case, the surface 631b and the surface 632 a, which face each other, are preferably flatsurfaces.

[0237] Moreover, in FIGS. 25A and 25B, an example is shown in which themultiple lens surfaces 606 a (631 a) of the fly-eye lens 606 each haspositive refraction power, but these lens surfaces may have negativerefraction power as well.

[0238] The prism array formed on the side of prism surface 606 b of thespecial fly-eye lens 606 includes, for example, a cluster body of afirst quad small prism set and a cluster body of a second quad smallprism set. The first quad small prism set is shown in FIG. 26A and thesecond quad small prism set is shown in FIG. 26B.

[0239] In FIG. 26A, the first small prism set comprises a prism surface606 b 1 with a normal line inclined towards the positive Z directionrelative to the XZ plane, a prism surface 606 b 2 with a normal lineinclined towards the positive X direction relative to the XZ plane, aprism surface 606 b 3 with a normal line inclined in the negative Zdirection relative to the XZ plane, and a prism surface 606 b 4 with anormal line inclined in the negative X direction relative to the XZplane.

[0240] In FIG. 26B, the second small prism set comprises a prism surface606 b 5 obtained by rotating the prism surface 606 b 1 by −45 around theY-axis, a prism surface 606 b 6 obtained by rotating the prism surface606 b 1 −135 around the Y-axis, a prism surface 606 b 7 obtained byrotating the prism surface 606 b 1 −225 around the Y-axis, a prismsurface 606 b 8 obtained by rotating the prism surface 606 b 1 −315around the Y-axis. In this example, clockwise rotation is defined to bethe positive direction.

[0241] Next, a case in which parallel light beams enter the specialfly-eye lens 606 is examined. In this case, multiple point light sourcesare formed on the exit side of the special fly-eye lens 606 due to thefunction of the multiple lens surface 606 a of the special fly-eye lens606. Moreover, because the front side (incidence side) of the focalposition of the zoom lens 607 is near the position of the multiple pointlight sources (rear side (exit side) focal position of the lens surface606 a), the multiple images of the lens surfaces 606 a are formedoverlapping each other on the rear side (exit side) focal plane of thezoom lens 607 which is positioned near the incident surface of thefly-eye lens 608. At this time, due to the function of the prismsurfaces 606 b 1-606 b 8 which are positioned corresponding to the lenssurface 606 a, the positions where the multiple images of the lenssurface 606 a are formed vary within the XZ plane.

[0242]FIG. 27A shows an illumination region that is formed on theincident surface of the fly-eye lens 608 by the light emitted from thespecial fly-eye lens 606 and transmitted through the zoom lens 607 whenparallel light beams enter the special fly-eye lens 606. In FIG. 27A,the illumination region 661 is formed by the light passing through theprism surface 606 b 1, the illumination region 662 is formed by thelight passing through the prism surface 606 b 2, the illumination region663 is formed by the light passing through the prism surface 606 b 3,the illumination region 664 is formed by the light passing through theprism surface 606 b 4, the illumination region 665 is formed by thelight passing through the prism surface 606 b 5, the illumination region666 is formed by the light passing through the prism surface 606 b 6,the illumination region 667 is formed by the light passing through theprism surface 606 b 7, and the illumination region 668 is formed by thelight passing through the prism surface 606 b 8.

[0243] Returning to FIG. 23, the diffractive optical device 604 diffusesthe parallel light beams from the light source 601 into light beams witha predetermined numerical aperture (divergence angle), and because theafocal zoom lens 605 makes the diffractive optical device 604 and thespecial fly-eye lens 606 to be nearly optically conjugate, the specialfly-eye lens 606 is illuminated by light beams with a numerical aperture(divergence angle) corresponding to the angle of magnification of theafocal zoom lens 605.

[0244] The diffractive optical device 606 generates light beams withcircular cross-section in the far field, and a cone-shaped body of lightbeams enter the special fly-eye lens 606. Here, cone-shaped light beamsentering the special fly-eye 606 may be considered to be a set of aninfinite number of light beams with multiple angular components. Hence,multiple illumination regions with slightly different positions in theXZ plane are formed on the incident surface of the fly-eye lens 608.FIGS. 27B and 27C show the circular illumination regions 671-678 and681-688 that are formed on the incidental surface of the fly-eye lens608.

[0245] One difference between FIG. 27B and FIG. 27C is that the verticalangles (divergence angle) of the cone-shaped light beams entering thespecial fly-eye lens 606 are different. FIG. 27B shows the state inwhich the light beams have a larger divergence angle than the lightbeams in FIG. 28C. By changing the divergence angle of light beamsentering the special fly-eye lens 606, the width of pseudo ring-shapedillumination regions (which includes clusters of circular illuminationregions 671-678 or 681-688) may be changed. In this case, the distanceRm between the center of the width of pseudo ring-shaped illuminationregions and the optical axis is constant. The divergence angle of thelight beams entering the special fly-eye lens 606 can be changed bychanging the angular magnification of the afocal zoom lens 605. In fact,the afocal zoom lens 605 is capable of changing the width of the rings.

[0246] Next, the function of the zoom lens 607 is described in referenceto FIG. 28A and FIG. 28B. FIGS. 28A and 28B respectively showillumination regions on the incident surface of the fly-eye lens 608. Bychanging focal length of the zoom lens 607, the illumination rangeenlarges or shrinks proportionally on the incident surface of thefly-eye lens 608. Here, FIG. 28A shows a condition in which the focallength of the zoom lens 607 is larger than the focal length in FIG. 28B.The angular magnification of the afocal zoom lens 605 is constant inboth states shown in FIGS. 28A and 28B.

[0247] By changing focal length of the zoom lens 607 in the abovemanner, the value of the outer radius Ro of the pseudo annular-shapeillumination region may be changed freely while keeping the ratio(annular ratio) of the inner radius Ri and the outer radius Ro of thepseudo annular-shape illumination regions formed in the illuminationregions 671-678 or 681-688 constant.

[0248] Moreover, by combining the changing of the angular magnificationof the afocal zoom lens 605 and the changing of the focal length of thezoom lens 607, the outer radius and the annular ratio of the pseudoannular-shape illumination region formed on the fly-eye lens 608 may beset to any desired values.

[0249] Because the fly-eye lens 608 forms a secondary light source witha shape corresponding to the shape of the illumination region on itsincident surface, the outer radius and the annular ratio of theannular-shaped secondary light source may be set to any desired valuesby changing the angular magnification of the afocal zoom lens 605 andthe focal length of the zoom lens 607.

[0250] Returning to FIG. 23, a variable aperture stop 609, a condenserlens 610, an illumination field stop 618, and an illumination field stopimaging optical system 619 are arranged. Light beams from the fly-eyelens 608 form an annular-shaped secondary light source whose shape isrestricted by a variable aperture stop 609. Light beams from theannular-shaped light source are overlapped in the condenser lens 610 andilluminate the illumination field stop 618. Moreover, the aperturesection of the illumination field stop 618 and a reticle 611 are in anearly conjugate relationship through the illumination field stopimaging optical system 619. Hence, an illumination region, which is animage of the aperture section of the illumination field stop 618, isformed on the reticle 611.

[0251] Here, the system from the reticle 611 to the wafer 613 similar tothe above embodiments, thus the description of the system is omitted.

[0252] The apparatus of FIG. 23 also includes a first driving system 622for mounting and removing the special fly-eye lens 606 relative to theillumination path, a second driving system 623 for moving at least oneof the plurality of lens groups composing afocal zoom lens 605 in thedirection of optical axis in order to change the magnification of theafocal zoom lens 605, a fourth driving system 625 for moving at leastone of a plurality of lens groups in the zoom lens 607 in the directionof optical axis in order to change the focal length of the zoom lens607, a fifth driving system for driving the variable aperture stop 609in order to specify the size and the shape of the surface light source(secondary light source), and a sixth driving system for driving thevariable aperture stop 617 in the projection optical system 612 in orderto specify a numerical aperture of the projection optical system 612.The apparatus in FIG. 23 also includes an input unit 620 for enteringinformation related to the type of reticle (mask), and a control system621 for controlling the aforementioned first-sixth driving systems622-627 based on the information from the input unit 620.

[0253] Sixth Embodiment

[0254]FIG. 29 is a schematic diagram of an illumination optical systemaccording to a sixth embodiment of the present invention. Light beamsfrom a light source 701, such as an excimer laser, are shaped into apredetermined shape by a beam expander 702 and are reflected by a mirror703 to a first diffractive optical device 751 attached to a revolver706A. Diffracted light beams from the first diffractive optical device751 are gathered by a relay lens 707 and uniformly and overlappinglyilluminate the incident surface of a fly-eye lens 708, which is awavefront dividing (splitting) type integrator. As a result, asubstantially surface light source is formed at the exit surface of thefly-eye lens 708. The relay lens 707 is an imaging optical system, andis designed in such a manner that the entire effective region near theexit side surface of the diffractive optical device 751 forms an imageover substantially the entire exit side surface of the fly-eye lens 708.

[0255] Light beams emitted from the surface light source at the exitside of the fly-eye lens 708 are gathered once overlappingly by thecondenser optical system 710 after the shape of the transmitted lightbeams have been restricted by the aperture stop 766 attached to arevolver 706B. Once the light beams are thus overlapped and pass throughthe relay optical system 712, they uniformly and overlappinglyilluminate the patterned reticle (or mask, original projection plate)714. An illumination field stop (reticle blind) 711 for determining theillumination region is arranged in the optical path between thecondenser optical system 710 and the relay optical system 712. Moreover,the projection optical system 715 projection exposes, using uniformillumination light, the pattern which is formed on the reticle 714 ontothe wafer 716.

[0256] The revolver 706A carries a plurality of diffractive opticaldevices 751, 752, 753 and a plurality of auxiliary fly-eye lenses 754,755, 756, as shown in FIG. 30A. Moreover, the revolver 706A isstructured in such a manner that the rotation of the revolver 706Aaround the optical axis AX by the driving motor MT1 enables theselection of the diffractive optical devices 751, 752, 753 and theauxiliary fly-eye lenses 754, 755, 756. Similarly, the aperture stops761-766 are structured in such a manner that stops with various apertureshapes are selected by the revolver 706B, as shown in FIG. 30B.

[0257] When the auxiliary fly-eye lenses 754-756 are selected byrotating the revolver 706A, the illumination optical system becomes adouble fly-eye lens system (double integrator system). The doublefly-eye lens system is capable of forming multiple three-dimensionallight source images matching the number m*n, a product of the number mof the lens elements in the auxiliary fly-eye lens and the number n ofthe lens elements in the fly-eye lens 708 on the exit surface of thefly-eye lens 708. Here, the auxiliary fly-eye lens 754 corresponds tothe aperture stop 765, the fly-eye lens 755 corresponds to the stop 763,and the fly-eye lens 756 corresponds to the stop 764. A technology forreducing the amount of light loss for circular aperture stops withdifferent diameters by switching the first fly-eye lens is disclosed,for example, in U.S. Pat. No. 5,392,094.

[0258] On the other hand, one of the merits of the present embodiment isthat the first through the third diffractive optical devices 751-753 arealso capable of being selected.

[0259] The first through third diffractive optical devices 751-753preferably are phase-type diffractive optical devices and are structuredby arranging a plurality of minute phase patterns and transmission ratepattern. FIG. 31A shows a cross-sectional shape of the diffractiveoptical device 751 viewed from the X direction. Light beams transmittedthrough the diffractive optical device 751 through the section denotedby A have a zero phase while the light beams transmitted through thesection denoted by B have a delay phase n. Hence, wave optically, thesetwo sets of light beams offset each other, resulting in thedisappearance of 0^(th) order light beams (direct transmission lightbeams), as shown in FIG. 31B. Hence, light beams transmitted through thediffractive optical device 751 are diffracted and transmitted throughthe relay lens 7 as ±first order diffracted light beams (or ±second andhigher order diffracted light beams). Moreover, light beams passingthrough the relay lens 707 become illumination having a delta functiontype intensity distribution I on the predetermined irradiation surfaceP, as shown in FIG. 31C. By using diffractive optical devices to whichvarious phase patterns and transmission rate patterns are added, thedesired light intensity distribution may be obtained on the irradiationsurface P, namely the incident surface of the fly-eye lens 708. Thediffractive optical device need not be arranged as shown in FIG. 31, butcan be any device that diffracts light beams through differences inphases, transmission rates and refraction rates.

[0260]FIG. 32A is an oblique view showing the incidence state of lightbeams into the first diffractive optical device 751 as one example. FIG.32B shows a state in which the diffraction light beams are viewed fromthe X direction, and FIG. 32C shows a state in which diffraction lightbeams are viewed from the Y direction. Here, assuming the optical axisto be the Z axis, and the vertical direction perpendicular to the Z axisto be the Y axis and the horizontal direction perpendicular to the Zaxis to be the X axis, the angle in the ZY plane is denoted by Θy andthe angle in the ZX plane is denoted by Θx. Because the incidental lightbeams are diffracted within the diffraction angle ranges of Θx0-Θx1 andΘy0-Θy1 due to the first order diffraction characteristics, thecross-sectional shape of the diffraction light beams become nearlyring-shaped. Moreover, an annular-shaped light intensity distribution isformed on the incident surface of the fly-eye lens 708 through the relaylens 707.

[0261]FIG. 33 is a diagram illustrating an illumination region that isformed on the incident surface of the fly-eye lens 708 by the firstdiffractive optical device 751. When the first diffractive opticaldevice 751 is used, the shape of the cross-section of the diffractedlight beams becomes nearly ring-shaped due to the first diffractioncharacteristics. Moreover, light beams transmitted through the relaylens 707 form a nearly uniform light intensity distribution only in thering-shaped illumination region IA denoted by the shaded area on theincident surface of the fly-eye lens 708. Here, the ring denoted by thedotted line is an aperture region AA formed by the aperture stop 766which is arranged along the optical axis AX corresponding to the firstdiffractive optical device 751. As the figure shows clearly, only theelement lenses 708 a of the fly-eye lens 708 corresponding to theaperture shape of the aperture stop 766 may be illuminated by thering-shaped light beams formed by the first diffractive optical device751 and the relay lens 707, and the light from the light source 701 maybe used with a high rate of efficiency.

[0262] The first diffractive optical device 751 may be made to onlyilluminate along the perimeter of element lenses 708 a that contributeto the light beams transmitting through the annular-shaped aperture stop766 in order to further increase the illumination efficiency. In thiscase, by altering the ranges of the diffraction angles Θx and Θy of thediffractive optical device 751 as needed, the multi-angle annular-shapedillumination region IA with different light intensity distributions atthe central section and at the perimeter region may be formed on theincident surface of the fly-eye lens 708. Hence, since only thenecessary element lenses 708 a are illuminated, the annular-shapedaperture stop 766 may be illuminated with extremely high efficiency.

[0263] Moreover, a diffractive optical device having diffractioncharacteristics that transform the diffraction light beams into apolygonal ring-shaped band with the outer shape of a barrel and theinner shape of a hexagon may be used as the first diffractive opticaldevice 751, as shown in FIG. 34B. In this case, an illumination regionIA is formed corresponding to the size of only those element lenses 708a used for illumination among all of the lenses in the fly-eye lens 708,enabling an increase in illumination efficiency while maintaininguniform illumination.

[0264] A diffractive optical device having diffraction characteristicsto transform into the illumination region IA with both an outer andinner shape of an elliptic ring band may be used as the firstdiffractive optical device 751, as shown in FIG. 34C. In this case, onlythe element lenses 708 a of all of the lenses in the fly-eye lens 708used for illumination are illuminated, resulting in an increase inillumination efficiency while maintaining uniform illumination.

[0265]FIG. 35 shows the relationship between the effective region of thediffractive optical device 751 and the element lenses 708 a of thefly-eye lens 708, with FIG. 35A showing the diffractive optical device751 and FIG. 35B showing part of the fly-eye lens 708. As the figuresclearly show, the effective region 751 a of the diffractive opticaldevice 751 and the XY cross-section of each of the element lenses 708Aof the fly-eye lens 708 are set to be both rectangular and similar. Bysetting them in this manner, the macroscopic structure of the lightpoint array LM that is formed at the exit surface of the fly-eye lens708 is most dense. In fact, the uniformity of the macroscopic lightintensity distribution at the position of the aperture stop 766 at theexit side of the fly-eye lens 708 may be improved, and further, theuniform illumination of reticle 714 and wafer 716 may be achieved.

[0266] The effective region 751 a of the diffractive optical device 751nearly coincides with the narrower one of the XY cross-section shape inthe vicinity of the exit surface of the region out of the diffractiondevice 751 or the XY cross-section shape of the incident beam enteringthe diffractive optical device 751. In the present embodiment, both theregion on which the optical element of the diffractive optical device751 is formed and the shape of incident beam entering the diffractiveoptical element 751 are made to coincide with the cross-sectional shapeof the element lenses 708 a in the fly-eye lens 708.

[0267] In changing the illumination conditions, the revolver 706B may berotated by the motor MT2, for example, so that the ring (annular)-shapedstop 763 with a larger diameter (the same shape but a different diameterthan the stop 766) shown in FIG. 30B may be placed in the optical path.When the aperture stop is switched to a ring-band stop with a largerdiameter in the above manner, the fly-eye lens 708 may be illuminatedwithout loss in a slight amount while keeping the first diffractiveoptical element 751, as long as the relay lens 7 is a variable focaldistance optical system (zoom optical system).

[0268] Moreover, when the revolver 706B is rotated by the motor MT2 andthe aperture stop 761 is selected, the revolver 706A is also rotated bythe motor MT1 to position the second diffractive optical device 752 inthe optical path. The second diffraction device 752 has seconddiffraction characteristics. The cross-sectional shape of light beamsdiffracted by the second diffraction light device 752 have a shape thatis scattered in four directions. Light beams form, after passing throughthe relay lens 707, an illumination region IA that has a light intensitydistribution with four regions on the incident surface in the fly-eyelens 708, as shown in FIG. 36A. Hence, useless illumination of thecross-shape region at the center is eliminated, resulting in highlyefficient illumination.

[0269] More preferably, when one of the four regions having a polygonalcross-section, particularly one with a pentagonal region such as thatshown in FIG. 36B, is used, optimum illumination corresponding to thesize of the element lenses 708 a in the fly-eye lens 708 is achieved,resulting in a further improvement in illumination efficiency whilemaintaining the uniformity of the illumination.

[0270] If each of the element lenses 708 a in the fly-eye lens isarranged randomly, namely not arranged in a lattice shape, optimumillumination corresponding to the size of the necessary element lenses708 a of all of the element lenses in the fly-eye lens 708 may beachieved by using a diffractive optical device having diffractioncharacteristics that make the outer shape of the four-region shapediffracted light into a polygonal shape.

[0271] When the present embodiment is applied to a scanning typeprojection exposure apparatus which performs exposure while moving thereticle as the original projection plate and the substrate as workrelative to the projection optical system, each shape of the pluralityof element lenses 708 a of the fly-eye lens 708 is preferably maderectangular. In this case, if the direction of the edge of theillumination region being formed on the fly-eye lens 708 is parallel tothe direction corresponding to the scanning direction (typically, thedirection along the minor side), the intensity distribution on the wafer716 may not be desirably distributed in the direction perpendicular tothe scanning direction.

[0272] For this reason, particularly with quadrupolar illumination, thedirections of the edges of four illumination regions formed on theincident surface of the fly-eye lens 708 by the diffractive opticaldevice 752 and by the relay lens 707 are preferably inclined in thedirections corresponding to the scanning direction of the plurality ofelement lenses 708 a of the fly-eye lens 708.

[0273] In FIG. 37A, the shapes of four illumination regions IA are madeto be elliptic in order to maintain the edges of the regions in thedirection that is continuously inclined relative to the scanningdirection in the element lenses 708 a. Moreover, FIG. 37B describes therelationship between the illumination region IA and the incidentsurfaces of the plurality of element lenses 708 a of the fly-eye lens708.

[0274] As FIG. 37B clearly shows, the edge of the elliptic illuminationregion IA does not intersect the plurality of the element lenses 708 aat the same location. Hence, unevenness (deviation from the desireddistribution) of the intensity distribution on the surface beingirradiated may be reduced.

[0275] In this case, using the aperture stop 766 on the exit side of thefly-eye lens 708, unevenness in illumination may be reduced even if theedges of the illumination regions in the plurality of the element lenses708 a that intersect are not shielded.

[0276] Furthermore, even if the aperture stop 766 is not used (or in thecase of the maximum aperture), uneven illumination may be reduced.Hence, even if the positions of a plurality of illumination regions arecontinuously changed using the relay lens 707 as a zoom optical system,it is unnecessary to continuously change the positions of aperture unitof the illumination aperture stop 766 corresponding to the illuminationregions.

[0277] Moreover, as shown in FIG. 37C, the shape of four illuminationregions IA may be made to be circular. From a point of view of improvingimaging performance, it is more preferable to make the shape of aplurality of illumination regions IA elliptic as shown in FIG. 37A thanto make them circular as shown in FIG. 37C, because it makes it possibleto separate the light amount distribution of the third order lightsource from the optical axis.

[0278] In a scanning type exposure apparatus, it is not necessary toconsider the direction of the edges of a plurality of the illuminationregions IA even if the direction is the same as the directionperpendicular to the scanning direction because the unevenness ofillumination along this direction is integrated by the scanningexposure. Hence, the shapes of a plurality of the illumination regionsIA which are formed by the diffractive optical device 752 and the relaylens 707 may be hexagonal, as shown in FIG. 37D. In this case, unevenillumination on the surface being irradiated may be reduced by settingthe system in such a manner that the edges of the illumination regionsIA intersect at an angle relative to the direction corresponding to thedirection of scanning of the element lenses 708 a.

[0279] The shape of the illumination regions are not limited tohexagonal, but other polygonal shapes may be used as long as the systemis set in such a manner that the edges of the illumination regionsintersect at angle relative to the direction corresponding to thedirection of scanning of the element lenses 708 a. In fact, the shape ofthe illumination regions IA may be rectangular as shown in FIG. 37E.

[0280] Moreover, even if the shape of the illumination regions ishexagonal, uneven illumination is not reduced, which is undesirable, aslong as the edges are parallel to the direction corresponding to thescanning direction of the element lenses 708 a (for example theillumination region IA shown in FIG. 37D is rotated 30 around its centerof gravity.)

[0281] In the above examples, four illumination regions are formed onthe incident surface of the fly-eye lens 708 assuming quadrupolarillumination, but the examples may be applied to multiple polarillumination such as octopolar illumination.

[0282] As described above, when a plurality of illumination regions areformed by the diffractive optical device and the relay lens on theincident surface of the wavefront dividing (splitting) type integrator,imaging performance may be improved and light loss may be reduced whilereducing uneven illumination on the surface being irradiated, by settingthe system in such a manner that the edges of a plurality ofillumination regions are inclined relative to the directioncorresponding to the scanning direction of the wavefront dividing(splitting) type integrator element lenses. Here, the imagingperformance may be further improved by setting the major axis of theillumination regions in the tangential direction (sagittal direction).

[0283] Application of this particular example may not be limited to thefifth embodiment, can be used with any of the embodiments describedabove and below.

[0284] Now, returning to FIG. 29, when the aperture stop 762 is selectedby rotating the revolver 706B, the third diffractive optical device 753is positioned in the optical path by rotating the revolver 706A. Thethird diffractive optical device 753 has third diffractioncharacteristics and across-section of the diffraction light beams arenear circular (barrel shaped) as shown in FIG. 38. Moreover, theillumination region IA, which is a near circular light intensitydistribution, is formed on the incident surface of the fly-eye lens 708through the relay lens 707. For this reason, the illumination efficiencymay be improved substantially compared to the case in which an auxiliaryfly-eye lens of the prior art is used.

[0285] Although three diffractive optical devices 751-753 with differentdiffraction characteristics and three auxiliary fly-eye lenses withdifferent focal lengths are used, only three diffractive optical devices751-753 with different diffraction characteristics may be used, ifdesired.

[0286] If each of the element lenses 708 a in the fly-eye lens 708 arearranged randomly, namely the element lenses are not arranged in alattice, optimum illumination for the size of the element lenses 708 aneeded in the fly-eye lens 708 may be achieved by arranging thediffractive optical device with diffraction characteristics to make theouter shape of the diffraction light beams polygonal. As a result, theamount of light loss may be reduced substantially while maintaininguniformity of the illumination.

[0287] The effective region of the first diffractive optical device 751is described above as being similar to the cross-section of the elementlenses 708 a of the fly-eye lens 708, but the effective regions of thesecond and the third diffractive optical devices 752, 753 can also berespectively similar to the cross-section of the element lenses 708 a ofthe fly-eye lens 708. Hence, even when the second and the thirddiffractive optical devices are selected with changes in illuminationconditions, the uniformity of the macroscopic light intensitydistribution at the positions of aperture stops 761, 762 on the exitside of the fly-eye lens 708 may be improved, and further, the uniformillumination of the reticle 714 and the wafer 716 may be achieved.

[0288] Next, a case in which both the first diffractive optical device751 with ring-shape divergent characteristics and a circular aperturestop 765 are used will be described.

[0289] In such combined illumination, the entire illumination region maybe utilized as far as the interior section of the ring band illuminationregion formed by the diffractive optical device 751 due to the absenceof an inner stop in the annular aperture. Hence, annular illuminationmay be achieved while holding light loss to a minimum. Combined use ofthe second diffractive optical device 752 having four-region dispersioncharacteristics and a circular stop 765 also results in a similar effectas a case in which the diffractive optical device 751 and the aperturestop 765 are used together.

[0290] Next, a method of arranging diffractive optical devices 751-753within the revolver 706A will be described. Each diffractive opticaldevice is stored in a protection container 770 as shown in FIG. 39. Theprotection container 770 includes a metal holder 770 a for supportingthe diffractive optical devices 751-753, and a cover glass 770 b whichis a pair of protective optical members anchored by and held parallel toeach other by the metal holder 770 a. In other words, the diffractiveoptical devices 751-753 are protected, in the direction of the opticalaxis, by the pair of cover glasses 770 b from foreign objects, such asgas generated by oxygen outside of the protection container 770 beingexcited by ultra-violet rays. In this case, the attachment of foreignobjects occurs only on the cover glass 770 b, hence, even if thetransmission rate deteriorates due to the attachment of the foreignobjects, the recovery of the transmission rate may be achieved by simplyreplacing the cover glass 770 b without replacing the relatively moreexpensive diffractive optical device 751-753.

[0291] Returning to FIG. 29, the diffraction surfaces of the diffractiveoptical devices 751-753 are preferably set at a position offset from afront focus of a relay optical system that guides the diffraction lightbeams from any of the diffractive optical devices 751-753 into thefly-eye lens 708 (optical integrator), along the optical axis direction.In such a structure, it becomes possible to reduce the interferencenoise (interference fringe) being generated on the reticle 714 or thewafer 716.

[0292] It is preferable that the fly-eye lens 708 has an upstream coverglass with an obscuration region on the optical axis. The obscurationregion shields the fly-eye lens 708 from 0^(th) order diffraction rayscaused by the diffractive optical device 751-753, and prevents thefly-eye lens 708 from damage.

[0293] Seventh Embodiment

[0294]FIG. 40 shows an illumination optical system in accordance with aseventh embodiment of the invention. The basic structure is similar tothe apparatus in the sixth embodiment, thus, the description of commonportions or features is omitted.

[0295] When the first through the third diffractive optical devices751-753 are positioned in the optical path, light beams passing throughthe diffractive optical device and irradiated onto the incident surfaceof the fly-eye lens 708 may result in a non-uniform illuminationintensity distribution due to the noise caused by a speckled pattern.Hence, a speckled pattern on the incident surface of the fly-eye lens708 is made to vibrate by vibrating the diffractive optical devices751-753 together with the revolver 706A by the vibration mechanical unitVB. As a result, the speckled pattern becomes averaged over the exposuretime period, and uniform light intensity distribution is obtained.

[0296] Furthermore, by arranging a v-shaped (a wedge shaped) deflectionprism DP between the relay lens 707 and the fly-eye lens 708, and byrotating the prism under exposure by the motor MT3 with the center ofsaid prism DP nearly coinciding with the optical axis AX, the lightintensity distribution formed on the incident surface of the fly-eyelens 708 may be rotated. As a result, the speckled pattern also isrotated and the speckled pattern becomes averaged over the exposure timeperiod, and light beams with uniform intensity may be obtained, as inthe case of vibrating the diffractive optical devices 751-753. Eitherthe vibration of the diffractive optical devices or the use of adeflection prism DP, or both may be adopted.

[0297] Moreover, in the case of the light source 701 emitting pulselight, the speckled pattern may become averaged by shifting or tiltingthe diffractive optical devices 751-753 over a predetermined number ofpulses.

[0298] Eighth Embodiment

[0299]FIG. 41A is a schematic drawing of a portion of the illuminationoptical system according to a eighth embodiment of the invention. Inthis example, at least the position or the posture of a portion of relaylens between two optical integrators is changed. As a result, at leastposition matching or changing the size of the illumination region on thedownstream optical integrator is executed, and adjustment of unevenillumination and adjustment of telecentricity are performed on thewafer. In FIG. 41A, only the structure between the upstream opticalintegrator (first optical integrator) and the downstream opticalintegrator (second optical integrator) is described.

[0300] In FIG. 41A, the relay optical system 807 which guides the lightbeams from the first optical integrator 805 to the second opticalintegrator comprises a front group 807 a and a rear group 807 b. Avibration mirror 807 c is also arranged between the front group 807 aand the rear group 807 b. In FIG. 41A, a folded optical path byvibration mirror 807 c is shown in an unfolded state. The front group807 a and/or the rear group 807 b are arranged in such a manner thatminute three dimensional motion and small rotation around a pair of axesperpendicular to the optical axis is enabled. A vibration mechanism 872is connected to the front group 807 a and/or the rear group 807 b andchanges the position and the posture of at least the front group 807 aor the rear group 807 b.

[0301] A driving mechanism 872 either moves the front group 807 a and/orthe rear group 807 b perpendicular to the optical axis, or tilts thefront group 807 a and/or the rear group 807 b relative to the opticalaxis to perform position matching between the illumination region formedby the first optical integrator and the incident surface of the fly-eyelens 808.

[0302] A driving mechanism 873 is also provided for the vibration mirror807 c to enable three dimensional minute movement or small rotationaround the pair of axes perpendicular to the optical axis of thevibration mirror 807 c. A driving mechanism that changes an angle of thevibration mirror 807 c during exposure time to reduce interference noiseis not shown here and is provided separately from the driving mechanism873. Position matching of the illumination regions on the second opticalintegrator may be performed by tilting the vibration mirror 807 crelative to the direction perpendicular to the optical axis.

[0303] The size of the illumination region on the incident surface ofthe fly-eye lens 808 may be adjusted by moving at least the front group807 a or the rear group 807 b toward the optical axis using the drivingmechanism 872. In this case, due to the movement of at least the frontgroup 807 a or the rear group 807 b toward the optical axis, thedeformation of the relay optical system 807 itself changes and theposition of the image formed by the relay optical system 807 movestoward the optical axis. Hence, the surface light source formed by thefly-eye lens 808 changes, enabling adjustment of at least unevenillumination or telecentricity on the wafer.

[0304] By appropriately operating driving mechanisms 872, 873 describedabove, uneven illumination and telecentricity may be adjusted accuratelyon the pattern surface of the reticle or on the exposure surface of thewafer. Here, telecentricity refers to the small amount of tilt of theillumination light beams entering the wafer 716 and the like, and to theimaging isotropy on the exposure surface and the like of wafer 716.Uneven illumination and telecentricity are adjusted by shifting ortilting the optical elements contained in the condenser optical systemprovided at the rear stage of the fly-eye lens 808, but even moreprecise adjustment is enabled by combining the minute movement of theoptical elements which constitute the relay lens 807 provided in thefront stage of the fly-eye lens.

[0305]FIG. 41B is a schematic drawing describing a portion of theillumination optical system of a variation of the eighth embodiment inan unfolded state. In this example, the relay optical system is made tobe a zoom optical system with a continuously variable focal length asopposed to the relay optical system being a fixed focal length opticalsystem.

[0306] In FIG. 41B, the relay optical system 907 which guides light fromthe first optical integrator 905 to the second optical integrator 908comprises, in the following order from the first optical integrator 905side, a positive lens group 907 a, a negative lens group 907 b, apositive lens group 907 c, and a positive lens group 907 d. Out of aplurality of lens groups 907 a-907 d, the lens groups 907 b-907 d areable to move in the direction of the optical axis along a predeterminedtrack denoted by an arrow in the figure. The focal length of the relayoptical system 907 is changed by the movement of the lens groups 907b-907 d.

[0307] At least one of the lens groups 907 a-907 d is structured to movein the direction of the optical axis independent of the aforementionedmovement for changing the focal length. By this movement, thedeformation of the relay optical system 907 itself is changed, and theposition, in the direction of optical axis, of the image formed by therelay optical system 907 also changes. As a result, the image beingformed on the second optical integrator 908 becomes out of focus and thesurface light source formed by the second optical integrator 908changes.

[0308] The driving mechanism 972 is connected to at least one of lensgroups 907 b-907 d which move in the direction of optical axis duringthe focal length change or the lens groups 907 a-907 d (at least one outof 907 a-907 d) which move along optical axis during defocusing. Thedriving mechanism 972 is controlled by a control system connected to theinput unit which receives information corresponding to the type ofreticle to be imaged. To be more specific, the control system controlsthe driving mechanism 972 so that the positions of a plurality of lensgroups 907 b-907 d are changed to the desired positions based oninformation corresponding to the type of reticle. Moreover, the drivingmechanism 972 changes the positions, in the direction of the opticalaxis, of each lens group 907 a-907 d.

[0309] At this time, the type of reticle or illumination condition, andthe position of each lens group may be stored beforehand in the memoryconnected to the control system, and control of said driving mechanism972 may be performed by referring to the data stored in said memory.Here, intensity distribution on the wafer surface may be measured andthe data stored in the memory may be updated using the results of themeasurement.

[0310] Moreover, instead of storing data in the aforementioned memoryrelating to the type of reticle or to the relationship between theposition of each lens group, data concerning the relationship betweenthe amount of movement of each lens group and the amount of change ofuneven illumination may be pre-stored, and each lens group may becontrolled to operate based on a relationship equation.

[0311] An illumination meter for measuring the intensity distribution onthe wafer surface is connected beforehand to a control system so thatthe position of each lens group may be changed depending on theintensity distribution on the wafer surface measured by the illuminationmeter.

[0312] At least one of the lens groups 907 a-907 d of the relay opticalsystem 907 may be made movable on the surface perpendicular to theoptical axis and/or made to be tiltable relative to the directionperpendicular to the optical axis.

[0313] Now, a case will be examined in which aforementioned diffractiveoptical device 751 is adopted as the first optical integrator 905. Inthis case, by changing the focal length of the relay optical system 907,the outer diameter of the annulus may be changed while maintaining theannular ratio of the illumination region formed on the second opticalintegrator 908 constant. Moreover, by defocusing the imaging position ofthe relay optical system 907, the annular ratio may be changed.

[0314] In this example, a four-group zoom lens was adopted for the relayoptical system 907, but a two-group zoom lens, three-group zoom lens orfive-group zoom lens may be adopted instead of the four-group zoom lens.In order to change the focal length while maintaining the position ofthe image from the relay optical system 907 itself constant, it issufficient to configure the relay optical system 907 with at least twomovable lens groups. In order to maintain the telecentricity at thesecond optical integrator 908 constant while maintaining the imageposition constant during the time of changing the focal length, themovable lens group in the relay optical system 907 is preferably athree- or larger group zoom lens.

[0315] In an illumination apparatus employing a wave surface splittingtype integrator and an inner surface reflection type integrator, theoptical system, for arranging the exit surface of the wave surfacesplitting type optical integrator and the incident surface of the innersurface reflection type integrator to be conjugate of each other, may bearranged between the two integrators. In applying such an illuminationapparatus to the above examples, it is sufficient to make the postureand/or the position of the portion of the optical system arrangedbetween the two integrators changeable.

[0316] Moreover, variations described above may be applied to any ofaforementioned embodiments. For example, in applying to the secondthrough fourth embodiments, the relay optical system 7 (or 7 a) betweenthe first fly-eye lens 6 and the second fly-eye lens 8 can be replacedwith the relay optical system 907.

[0317] As applied to the first embodiment, the relay optical system 7between the diffractive optical device 6 and the first fly-eye lens 8can be replaced with the relay optical system 907.

[0318] As applied to the fifth embodiment shown in FIG. 23, the relayoptical system 607 between the specialty fly-eye lens 606 and thefly-eye lens 608 can be replaced with the relay optical system 907.

[0319] As applied to the sixth embodiment, the relay optical system 707between the diffractive optical device 751 (-753) and the fly-eye lens708 can be replaced with the relay optical system 907.

[0320] It is also possible to combine the first through eighthembodiments mentioned above.

[0321] Ninth Embodiment

[0322]FIG. 42 is a schematic diagram of an illumination optical systemof an ninth embodiment of the invention. In this example, the microfly's eye lens 4 of the first embodiment, diffractive optical device 6 bof the third embodiment, and the diffractive optical device 753 of thesixth embodiment are attached to a turret T1. One of these devices isselected and inserted within illumination optical path. Moreover, thediffractive optical device 6 of the first embodiment and the fly-eyelens (micro fly's eye lens) 4 of the third embodiment are attached to aturret T2. Moreover, the turret T2 also contains an aperture (hole) H.One of these devices and the hole H is selected and arranged within theillumination optical path.

[0323] Plural sets of magnification relay optical systems Re1, Re2 andan optical path delaying optical system RT are arranged between thelaser light source 1 and the turret T1. The optical path delayingoptical system is described in Japanese Unexamined Patent PublicationNo. Hei. 11-174365, and U.S. patent application Ser. No. 09/300,660,filed Apr. 27, 1999, which are hereby incorporated by reference in theirentirety. The afocal zoom optical system 5 described in the firstthrough fourth embodiments is arranged between the turret T1 and theturret T2, and a zoom optical system 7 is arranged between the turret T2and the fly-eye lens 8.

[0324] By setting the micro array lens 4 on the turret T1 and thediffractive optical device 6 on the turret T2 on the illuminationoptical path, annular illumination is obtained. Moreover, by setting thediffractive optical device 6 b on the turret T1 and the fly-eye lens 4on the turret T2 in the illumination optical path, quadrupolarillumination is obtained. By setting the diffractive optical device 753on the turret T1 and the hole H on the turret T2 in the illuminationoptical path, a regular circular illumination is obtained.

[0325] Tenth Embodiment

[0326]FIG. 43 is a schematic diagram of an illumination optical systemin accordance with a tenth embodiment of the invention.

[0327] The light source 101 is preferably either KrF (oscillationwavelength 248 nm) or ArF excimer laser light source (oscillationwavelength 193 rim), but other light sources can be used. Nearlyparallel light beams emitted from the light source 1001 in the directionof the Y-axis enter the diffractive optical device 1004 through amagnification relay optical system 1002.

[0328] The diffractive optical device 1004 transforms and emits theentering excimer laser beam with a rectangular cross-section to have anearly ring shaped cross-section in the far field (Fraunhoferdiffraction region) of the diffractive optical device 1004. Thediffractive optical device 1004 is equivalent to the diffractive opticaldevice 751 of the sixth embodiment. Here, the diffractive optical device1004 is provided in such a manner that it is interchangeable with thediffractive optical device 1004 b which is equivalent to the diffractiveoptical device 752 in the sixth embodiment and with the diffractiveoptical device 1004 c, which is equivalent with the diffractive opticaldevice 753.

[0329] In the lower side of the diffractive optical device 1004, lensgroup 1005A, a concave prism member 1005B with a concave cone shaperefraction surface, a convex prism member 1005C with a convex conerefraction surface facing the concave surface of the concave prismmember 1005B, and an annular ratio variable optical system 1005 with alens group 1005D are arranged.

[0330] The convex prism member 1005C is movable in the direction alongthe optical axis of the illumination apparatus. Instead of moving theconvex prism member 1005C, the concave prism member 1005B may be moved,or both the concave prism member 1005B and the convex prism member 1005Cmay be moved. Here, the order of the concave prism member 1005B and theorder of the convex prism member 1005C may be reversed.

[0331] Downstream of the annular ratio variable optical system 1005, azoom optical system 1007 with a plurality of lens groups is arranged. Azoom optical system equivalent of the zoom optical system 907 in theeighth embodiment is used, for example, as the zoom optical system 1007.

[0332] Downstream of the zoom optical system 1007, a fly-eye lens 1008is arranged as a wave surface splitting type optical integrator, anddownstream of the fly-eye lens 1008, a variable aperture stop 1009 isarranged.

[0333] At the exit side of the fly-eye lens 1008, a variable aperturestop 1009, a condenser lens 1010, an illumination field stop 1018 and anillumination field stop imaging optical system 1019 are arranged. Lightbeams from the fly-eye lens 1008 form an annular shaped surface lightsource due to the function of the variable aperture stop 609 whichrestricts a portion of the light beams. Light beams from the annularshaped surface light source, after being overlapped by the condenserlens 1010, illuminate the illumination field stop 1018. The apertureunit of the illumination field stop 1018 and the reticle 1011 aresubstantially in a conjugate relationship due to the illumination fieldstop imaging optical system 1019, and the illumination region, which isan image of the aperture unit of the illumination field stop 1018, isformed on the reticle 1011.

[0334] In this instance, the systems from the reticle 1011 to the wafer1013 are similar to each of aforementioned embodiments, hence anyfurther explanation is omitted.

[0335] Now, the conjugate relationship of each member will be described.First, the variable aperture stop 1009 is arranged at the pupil surfaceof the illumination apparatus, and the positions nearly conjugate to thepupil surface of the illumination apparatus are the front side (incidentside) focal plane of the zoom optical system 1007, the diffractionsurface of the diffractive optical device 1004, and the pupil of theillumination field stop imaging optical system 1019. Here, thediffraction surface of the diffractive optical device 1004 may be set atthe defocus position relative to the pupil conjugate surface.

[0336] The incident surface of the fly-eye lens 1008 is positioned at aposition conjugate to the wafer 1013, and the positions nearly conjugateto the wafer 1013 are the pupil surface of the annular ratio variableoptical system 1005 (the surface on which the rear focus of the lens(group) 1005A and the front focus of the lens (group) 1005D coincide),the incident surface of said fly-eye lens 1008 and the illuminationfield stop 1018, and the pattern surface of the reticle 1011.

[0337] In the annular ratio variable optical system 1005, the concavecone prism 1005B receives light beams in a nearly annular shapedcross-section which are diffracted by the diffractive optical device1004. By changing the distance between the concave cone prism 1005B andthe convex cone prism 1005C, the angle of light beams emitted from theannular ratio variable optical system 1005 to the zoom optical system1007 is changed.

[0338] Once the angle of light beams received by the zoom optical system1007 is changed, the outer diameter (inner diameter) is changed whilethe width of the annulus of the annular shape illumination region formedin the vicinity of the incident surface of the fly-eye lens 1008 ismaintained constant. Moreover, when the focal length of the zoom opticalsystem 1007 is changed, the outer diameter (inner diameter) is changed,while the annular ratio (the ratio of the inner diameter and the outerdiameter of the ring) of the annular shape illumination region formed inthe vicinity of the incident surface of the fly-eye lens 1008 ismaintained constant.

[0339] As a result, the annular shaped illumination region formed on theincident surface of the fly-eye lens 1008 may be changed to have anarbitrary outer diameter (inner diameter) and an arbitrary annular ratioby combining the movement of the prism member in the annular ratiovariable optical system 1005 and the motion to change the focal lengthof the zoom optical system 1007. Furthermore, the outer diameter (innerdiameter) and the annular ratio of the annular shaped secondary lightsource formed on the exit side of the fly-eye lens 1008 may be set toarbitrary values.

[0340] A first driving system 1022 for interchanging the diffractiveoptical devices 1004, 1004 b, 1004 c, a second driving system 1023 forchanging the distance between prism members 1005B and 1005C in theannular ratio variable optical system 1005 in order to change the angleof light beams from the annular ratio variable optical system 1005, afourth driving system 1025 for moving at least one of the plurality oflens groups in the zoom lens 1007 in the direction of the optical axisin order to change the focal length of the zoom lens 1007, a fifthdriving system 1026 for driving the variable aperture stop 1009 tospecify the size and the shape of the surface light source (secondarylight source), and a sixth driving system 1027 for driving the variableaperture stop 1017 in the projection optical system 1012 to specify theaperture number of the projection optical system 1012. An input unit1020 for entering information concerning the type of reticle (mask), anda control system 1021 for controlling said first-sixth driving systems1022-1027 based on the information from the input unit 1020 are alsoprovided.

[0341] When performing quadrupolar (multi-polar) illumination, thediffractive optical device 1004 b is inserted in the illumination path.In this case, the positions of four illumination regions formed on theincident surface of the fly-eye lens 1008 may be changed by controllingthe distance between the prism members 1005B and 1005C in the annularratio variable optical system 1005, and the sizes of the fourillumination regions may be changed by changing the focal length of thezoom optical system 1007.

[0342] By controlling these two optical systems (the annular ratiovariable optical system 1005 and the zoom optical system 1007), the sizeand the distance from the optical axis of four surface light sourcesformed at the pupil position of the illumination apparatus may beadjusted freely.

[0343] In performing quadrupolar illumination, a pyramid shaped prismmember is preferably used instead of a cone shape prism member. In thiscase, interchanging the cone-shaped prism member with a pyramid shapedprism member may be automatically executed with the interchanging of thediffractive optical devices.

[0344] When performing normal illumination, the diffractive opticaldevice 1004 c is inserted in the illumination optical path by the firstdriving system 1022. In this case, the size of the circular surfacelight source formed at the pupil position of the illumination apparatusmay be adjusted freely by changing the focal length of the zoom opticalsystem 1007.

[0345] In each of the embodiments above, the downstream-most opticalintegrator preferably has a wave splitting number (integral number) of300 or larger. Thus, unevenness of illumination on the surface beingirradiated may be reduced by the aperture unit of the illuminationaperture stop arranged on the exit side of the optical integrator, evenif the edge section of the surface light source including many lightsources formed by the wave surface splitting type optical integrator isnot specified.

[0346] The reasons for above are described hereafter. First, the case inwhich the shape of each of a plurality of element optical systems (aplurality of lens surfaces or a plurality of reflection surfaces) issquare and in which a circular irradiation region is formed on theincident surface of the wave surface splitting type optical integratorwill be examined. In this case, the integral number N (the number ofwave surface splits) of the wave surface splitting type opticalintegrator is given by the formula:

N=π(R ² /d ²)  (16)

[0347] where d is the length of the side of the element optical systemand R is the radius of the irradiation region.

[0348] In the wave surface splitting region (corresponding to theirradiation region above) of the wave surface splitting opticalintegrator, the number Ns of the splitting regions which exist aroundthe perimeter is given by the formula:

Ns=2π(R/d)  (17)

[0349] Here, the interior of the splitting regions that exist around theperimeter may suffer uneven illumination with a maximum unevenillumination in one splitting region around the perimeter being 100%.However, the intensity of light beams reaching the splitting regionsaround the perimeter is weaker than the regions around the center.Hence, the effect of uneven illumination becomes small and the degree ofthe absolute effect on the surface being irradiated also becomes small.

[0350] Based on a comprehensive analysis of the above factors, unevenillumination which occurs in one split region around the perimeter maybe estimated as {fraction (1/3)} the unevenness of that in the regionaround the center. Moreover, due to the statistical randomness in theregions around the perimeter, the square root of the number Ns of thesplitting regions around the perimeter may have an effect on unevenillumination on the surface being irradiated.

[0351] Hence, in order to reduce the uneven illumination on the surfacebeing irradiated to 1% or less, the condition;

(({fraction (1/3)})Ns ^((1/2)))/N<0.01  (18)

[0352] is preferably satisfied. Substituting (16) and (17) above in(18),

N>249  (19)

[0353] is obtained.

[0354] Hence, the wave surface splitting number by the opticalintegrator must exceed about 300 in order to control uneven illuminationon the surface being irradiated, which leads to even control of unevenillumination on the surface being irradiated, and particularly when, theillumination conditions are changed.

[0355] In an optical integrator of the illumination apparatus which isapplied to a scanning type exposure apparatus, the shape of the elementoptical system is rectangular, but an argument similar to above argumentmay be applied. Moreover, the argument used above is based on theintegrator in which the element optical system such as fly-eye lenses isarranged in a two-dimensional matrix, but the above argument may beapplied to an inner reflection type integrator such as a rod-typeintegrator (light pipe, light tunnel, glass rod).

[0356] In conclusion, in an illumination apparatus employing an opticalintegrator which splits incidental light beams from the light source andwhich uses the split light beams to illuminate the surface beingirradiated overlappingly, the integral number for the optical integratoris preferably set to be 300 or larger. As a result, changes in unevenillumination on the surface being irradiated may be minimized even ifthe illumination regions on the incident surface (the opening angle(aperture angle) of incident light beams in the case of a wave surfacesplitting type optical integrator and in the case of an inner reflectiontype integrator) of the optical integrator change.

[0357] The following explains one example of operation when forming apredetermined circuit pattern on a wafer using an exposure apparatus ofthe above embodiments with reference to the flowchart 99 shown in FIG.44.

[0358] First, after the “start” step 100, in step 101, metal films aredeposited onto each wafer in a lot of wafers. In step 102, photoresistis coated onto the metal films of each wafer in the lot of wafers.Subsequently, in step 103, using the exposure apparatus of any one ofabove embodiments, the image of the pattern on the reticle issequentially exposed and transferred onto the photoresist(photosensitive material) on each exposure region on each wafer.Subsequently, in step 104, the photoresist on each wafer in the lot ofwafers is developed. By performing etching using the resist patterns asa mask in step 105, the circuit pattern corresponding to the pattern onthe reticle is formed in each exposure region on each wafer.Subsequently, the manufacture of devices like a semiconductor device iscompleted by further forming circuit patterns on upper layers, asindicated by step 106, “next process.”

[0359] In addition, detailed description of the diffractive opticalelement that can be used in above embodiments is disclosed in U.S. Pat.No. 5,850,300, which is hereby incorporated by reference in itsentirety.

[0360] In the above embodiments, it is possible to form the diffractiveoptical element for example of silica glass because exposure lighthaving a wavelength of not less than 180 nm is utilized by using as thelight source a KrF excimer laser (wavelength: 248 nm) or an ArF excimerlaser (wavelength: 193 nm) or the like.

[0361] When a wavelength of 200 nm or less is used for the exposurelight, it is preferable for the diffractive optical element to be formedof material selected from among fluorite, silica glass doped withfluorine, silica glass doped with fluorine and hydrogen, silica glasswith a structure determining temperature of 1200K or less and anOH-radical concentration of 1000 ppm or greater, silica glass with astructure determining temperature of 1200K or less and a chlorineconcentration of 50 ppm or less, and silica glass with a structuredetermining temperature of 1200K or less and a hydrogen moleculeconcentration of 1×10¹⁷ molecules/cm³ or greater and a chlorineconcentration of 50 ppm or less.

[0362] Silica glass with a structure determining temperature of 1200K orless and an OH-radical concentration of 1000 ppm or greater is disclosedin Japanese patent 2,770,224 (which corresponds to European patent720970 B) by the present applicant, while silica glass with a structuredetermining temperature of 1200K or less and a hydrogen moleculeconcentration of 1×10¹⁷ molecules/cm³ or greater, silica glass with astructure determining temperature of 1200K or less and a chlorineconcentration of 50 ppm or less, and silica glass with a structuredetermining temperature of 1200K or less and a hydrogen moleculeconcentration of 1×10¹⁷ molecules/cm³ or greater and a chlorineconcentration of 50 ppm or less are disclosed in Japanese patent2,936,138 (which corresponds to U.S. Pat. No. 5,908,482) by the presentapplicant.

[0363] In addition, in the above described embodiments, the fly-eye lens8, 608, 708, 808, 908 and 1008 are formed by integrating a plurality ofelement lenses, but it is also possible to make this a micro fly-eyelens. A micro fly-eye lens is created by providing a plurality ofmicrolens surfaces in a matrix shape through a method such as etching orthe like on an optically transmissive substrate. With regard to forminga plurality of light source images, there is no material difference infunction between a fly-eye lens and a micro fly-eye lens, but a microfly-eye lens has the benefits of enabling the size of the aperture of asingle element lens (microlens) to be made extremely small, allowing alarge reduction in production costs and greatly reducing the thicknessin the optical axis direction. Moreover, the microlens surface on theincident and/or exit sides can be formed in an aspherical shape.

[0364] In the above-mentioned embodiments, a zoom optical system havingthe numerical value example shown in FIG. 45 can be used as the zoomoptical systems 7, 607, 707 and 710. FIGS. 45A-D are diagrams showingthe movement path of the respective lens groups along with the change ofthe focal length from a maximum focal length state to a minimum focallength state of the zoom optical system according to the first numericalvalue embodiment. FIG. 45A shows a maximum focal length state (focallength F=570 mm). FIG. 45B shows a first intermediate focal length state(focal length F=380 mm). FIG. 45C shows a second intermediate focallength state (focal length F=285 mm). FIG. 45D shows a minimum focallength state (focal length F=190 mm).

[0365] The zoom optical system relating to this numerical valueembodiment has a first lens group G1 having a positive refractive power,a second lens group G2 having a negative refractive power, a third lensgroup G3 having a positive refractive power, and a fourth lens group G4having a negative refractive power.

[0366] Furthermore, in the zoom optical system of this numerical valueembodiment, with respect to a change of the focal length from themaximum focal length state to the minimum focal length state, the firstlens group G1 through the third lens group G3 move along the paths shownin FIGS. 45A-D, and the fourth lens group G4 is fixed. That is, withrespect to a change of a focal length from the maximum focal lengthstate to the minimum focal length state, the first lens group G1 movestoward the image side (downstream fly eye lens 8 side), and the secondlens group G2 moves toward the object side (the upstream side).Furthermore, in the minimum focal length state, the first lens group G1and the second lens group G2 approach each other.

[0367] Furthermore, with respect to a change of the focal length fromthe maximum focal length state to the minimum focal length state, thethird lens group G3 moves toward the object side from a position (inFIG. 45A) where it approached the fixed fourth lens group G4.

[0368] Thus, in the zoom optical system of this numerical valueembodiment, the interval between the first lens group G1 and the secondlens group G2 in the maximum focal length state is larger than theinterval between G1 and G2 in the minimum focal length state, and theinterval between the third lens group G3 and the fourth lens group G4 inthe maximum focal length state is smaller than the interval between G3and G4 in the minimum focal length state.

[0369] Thus, in the zoom optical systems of this numerical valueembodiment, when it is considered that an aperture diaphragm is arrangedat a position in which the light source image (secondary light source)is formed and the incident surface of the fly eye lens 8 is an imageplane, the structure is such that the positions of the exit pupil and ofthe entrance pupil and the positions of the image plane and the objectplane do not substantially change when the focal length changes.

[0370] The following Table 3 shows lens data of a zoom optical system ofthis numerical value embodiment. In Table 3, F is the focal length ofthe zoom optical system, f1 is the focal length of the first lens groupG1, f2 is the focal length of the second lens group G2, f3 is the focallength of the third lens group G3, and f4 is the focal length of afourth lens group G4. Furthermore, d1 is an axial variable intervalbetween an aperture diaphragm (light source image formation position,which is pupil conjugate position) and the first lens group G1, d3 is anaxial variable interval between the first lens group G1 and the secondlens group G2, d5 is an axial variable interval between the second lensgroup G2 and the third lens group G3, and d13 is an axial variableinterval between the third lens group G3 and the fourth lens group G4.Furthermore, the surface numbers are the respective lens surfaces alongthe direction in which the light beam proceeds, r is the radius ofcurvature (mm) of the respective surfaces, d is the axial interval, thatis, a surface interval (mm) of the respective surfaces, and n is therefractive index with respect to wavelength of exposure light. TABLE 3(General system data) Focal length F: 570 mm˜380 mm˜285 mm˜190 mm Zoomratio: 3 Aperture diaphragm diameter φ (Diameter): 60 mm Light beamincident angle to the aperture diaphragm A: 0°, 2.5°, 3.6°, 5.1° (Lensdata) Surface number r d n 1 (Aperture (d1 = Variable) diaphragm) 2171.43815 18.000000 1.50839 (First lens group 3 −1132.08474 (d3 =Variable) G1) 4 171.92962 10.000000 1.50839 (Second lens group G2) 564.53113 (d5 = Variable) 6 −60.25508 13.000000 1.50839 (Third lens groupG3) 7 723.78037  8.551388 8 −675.45783 30.000000 1.50839 9 −110.00000 1.000000 10 1541.19265 40.000000 1.50839 11 −130.00000  1.000000 12288.43523 30.000000 1.50839 13 −274.48506 (d13 = Variable) 14−1242.27153 13.000000 1.50839 (Fourth lens group G4) 15 173.4691260.000000 16 (Image plan) (Variable interval for zooming) Firstintermediate Maximum Minimum focal Second intermediate focal lengthfocal length state focal length state state length state F 190.0 285.0380.0 570.0 d1 77.96687 24.25432 10.00000 10.00000 d3 15.00000 105.08205145.98277 172.83221 d5 40.00000 42.40557 51.65276 81.87262 d13 142.49166103.70659 67.81301 10.74371

[0371] Furthermore, the following Table 4 shows ray tracing data for alight beam that has an incident angle A on the aperture diaphragm of 0°,a light beam (R1) with an incident angle A of 2.5°, a light beam (R2)with an incident angle A of a 3.6°, and a light beam (R3) with anincident angle A of 5.1°.

[0372] In Table 4, θ is the angle of the chief ray (the light beamcrossing the optical axis in the aperture diaphragm), with respect tothe optical axis, and Y is the distance, that is, the image height, fromthe optical axis of the chief ray that reaches the image plane.Furthermore, the inclination angle of the chief ray at the image planeis the inclination angle of the chief ray with respect to the opticalaxis at the image plane. TABLE 4 (Maximum focal length state) Focallength F 570 mm Axial interval between the aperture diaphragm and 500 mmthe image plane Inclination angle of the chief ray at the image plane5.4′ (R1: θ = 2.5°) Inclination angle of the chief ray at the imageplane 4.5′ (R2: θ = 3.6°) Inclination angle of the chief ray at theimage plane 4.7′ (R3: θ = 5.1°) Image height Y 24.9 mm (R1: θ = 2.5°)Image height Y 35.8 mm (R2: θ = 3.6°) Image height Y 50.7 mm (R3: θ =5.1°) (First intermediate focal length state) Focal length F 380 mmAxial interval between the aperture diaphragm and 500 mm the image planeInclination angle of the chief ray at the image plane 3.0′ (R1: θ =2.5°) Inclination angle of the chief ray at the image plane 3.0′ (R2: θ= 3.6°) Inclination angle of the chief ray at the image plane 0.4′ (R3:θ = 5.1°) Image height Y 16.6 mm (R1: θ = 2.5°) Image height Y 23.9 mm(R2: θ = 3.6°) Image height Y 33.8 mm (R3: θ = 5.1°) (Secondintermediate focal length state) Focal length F 285 mm Axial intervalbetween the aperture diaphragm and 500 mm the image plane Inclinationangle of the chief ray at the image plane 5.2′ (R1: θ = 2.5°)Inclination angle of the chief ray at the image plane 6.9′ (R2: θ =3.6°) Inclination angle of the chief ray at the image plane 7.9′ (R3: θ= 5.1°) Image height Y 12.4 mm (R1: θ = 2.5°) Image height Y 17.9 mm(R2: θ = 3.6°) Image height Y 25.3 mm (R3: θ = 5.1°) (Minimum focallength state) Focal length F 190 mm Axial interval between the aperturediaphragm and 500 mm the image plane Inclination angle of the chief rayat the image plane 3.0′ (R1: θ = 2.5°) Inclination angle of the chiefray at the image plane 4.8′ (R2: θ = 3.6°) Inclination angle of thechief ray at the image plane 8.1′ (R3: θ = 5.1°) Image height Y 8.3 mm(R1: θ = 2.5°) Image height Y 11.9 mm (R2: θ = 3.6°) Image height Y 16.8mm (R3: θ = 5.1°)

[0373] Furthermore, if the light beam incident upon the fly eye lens 8that follows the zoom optical system is inclined with respect to theoptical axis of the respective lens elements of the fly eye lens 8,eclipse of the light beam is generated at the exit surface of the flyeye lens 8 and the effectiveness of illumination deteriorates. Accordingto a general design example, in order to substantially avoid eclipse ofthe light beam at the emitting surface of the fly eye lens 8, theinclination angle needs to be within approximately ±5° with respect tothe optical axis of the chief ray at the image plane of the zoom opticalsystem, and preferably within approximately ±1° in order to properlysuppress the change of the illumination distribution on the mask.

[0374] With reference to Table 4, in the zoom optical system of thenumerical value embodiment, the inclination angle is extremely smallwith respect to the optical axis of the chief ray at the image plane,and the position of the exit pupil hardly changes from an infinitedistance when the focal length changes. Additionally, there isabsolutely no change in the position of the image plane when the focallength changes. In addition, needless to say, there is absolutely nochange in the position of the entrance pupil as well.

[0375] Thus, in the zoom optical system of this numerical valueembodiment, all the lens components are arranged toward the image planefrom the pupil plane, and a desired zoom ratio can be secured withoutsubstantially changing the positions of the emitting pupil and theincident pupil and the positions of the image plane and the object planewith respect to the change of the focal length.

[0376] Furthermore, in the above-mentioned numerical value example, apositive•negative•positive•negative refractive power arrangement wasused, but a negative•positive•negative•positive refractive powerarrangement can also be used as shown in the following Table 5. TABLE 5(General system data) Focal length F: 600 mm˜400 mm˜300 mm˜200 mm Zoomratio: 3 Aperture diaphragm diameter φ (Diameter): 60 mm Light beamincident angle A to the aperture diaphragm A: 0°, 2.4°, 3.3°, 4.8° (Lensdata) Surface number r d n 1 (Aperture (d1 = Variable) diaphragm) 2−185.06450 13.000000 1.50839 (First lens group G1) 3 3586.41632 (d3 =Variable) 4 384.28464 27.438625 1.50839 (Second lens group G2) 5−271.20132  1.000000 6 97.04956 39.694311 1.50839 7 −2482.11415 1.000000 8 93.60504 21.938153 1.50839 9 144.92710 17.078265 10−219.42806  8.000000 1.50839 11 52.67801 (d11 = Variable) 12 −100.3117513.000000 1.50839 (Third lens group G3) 13 −199.93788 (d13 = Variable)14 713.30899 21.983709 1.50839 (Fourth lens group G4) 15 −168.6155360.000000 16 (Image plane) (Variable interval for zooming) Firstintermediate Maximum Minimum focal Second intermediate focal lengthfocal length state focal length state state length state F 200.0 300.0400.0 600.0 d1 29.834241 8.531256 15.409789 8.531256 d3 176.157154121.422675 70.994410 10.000000 d11 60.419144 30.985358 60.209359162.073170 d13 9.456398 114.927649 129.253380 95.262510

[0377] While the present invention has been described with reference topreferred embodiments thereof, it is to be understood that the inventionis not limited to the disclosed embodiments or constructions. To thecontrary, the invention is intended to cover various modifications andequivalent arrangements. In addition, while the various elements of thedisclosed invention are shown in various combinations andconfigurations, that are exemplary, other combinations andconfigurations, including more, less or only a single element, are alsowithin the spirit and scope of the invention.

What is claimed is:
 1. An illumination system for illuminating a surfaceby use of light from a light source, the illumination system comprising:an emission angle conserving optical unit effective to emit the lightfrom the light source at a constant divergent angle; and a diffractiveoptical element for producing a desired light intensity distribution ona predetermined plane, wherein the diffractive optical element isdisposed at or adjacent to a position where light from the emissionangle conserving optical unit is collected.
 2. The illumination systemaccording to claim 1, further comprising a multiple-beam producingelement, and a light projecting element for superposing light beams fromthe multiple-beam producing element one upon another on the surface tobe illuminated, wherein the predetermined plane corresponds to a lightentrance surface of the multiple-beam producing element.
 3. Theillumination system according to claim 2, further comprising a zoomoptical system for projecting the light intensity distribution, producedby the diffractive optical element, upon the light entrance surface ofthe multiple-beam producing element at a predetermined magnification. 4.The illumination system according to claim 3, wherein a plurality ofemission angle conserving optical units of different divergent anglesare provided, and wherein the emission angle conserving optical unitsare interchangeably set at a light path in accordance with a change inmagnification of the zoom optical system.
 5. The illumination systemaccording to claim 1, wherein a plurality of diffractive opticalelements for producing different light intensity distributions on thepredetermined plane are provided, wherein the diffractive opticalelements are interchangeably set at a light path to produce a desiredlight intensity distribution on the predetermined plane.
 6. Theillumination system according to claim 1, wherein the diffractiveoptical element is a phase type.
 7. The illumination system according toclaim 1, wherein the emission angle conserving optical unit comprises aflys eye lens having small lenses arrayed two-dimensionally.
 8. Anexposure apparatus, comprising: an illumination optical system forilluminating a mask surface, as a surface to be illuminated, with use oflight from a light source, the illumination optical system including (i)an emission angle conserving optical unit effective to emit the lightfrom the light source at a constant divergent angle, and (ii) adiffractive optical element for producing a desired light intensitydistribution on a predetermined plane, wherein the diffractive opticalelement is disposed at or adjacent to a position where light from theemission angle conserving optical unit is collected; and a projectionoptical system for projecting a pattern formed on the mask surface, asilluminated with the light from the illumination optical system, onto awafer.
 9. A device manufacturing method, comprising the steps of:applying a photosensitive material to a wafer; illuminating a masksurface, as a surface to be illuminated, with use of light from anillumination optical system, wherein the illumination optical systemincludes (i) an emission angle conserving optical unit effective to emitthe light from the light source at a constant divergent angle, and (ii)a diffractive optical element for producing a desired light intensitydistribution on a predetermined plane, wherein the diffractive opticalelement is disposed at or adjacent to a position where light from theemission angle conserving optical unit is collected; projecting, througha projection optical system, a pattern formed on the mask surface onto awafer; and developing the transferred pattern.
 10. An illuminationsystem for illuminating a surface by use of light from a light source,the illumination system comprising: an optical integrator which isarranged in a light path of the illumination system; an illuminationpupil having a light intensity distribution such that a lower lightintensity is formed at a position near an optical axis relative topositions away from the optical axis; an annular ratio changer which isarranged in an optical path between the light source and the opticalintegrator and which changes the annular ratio of the light intensitydistribution; and an outer diameter changer which is arranged in anoptical path between the light source and the optical integrator andwhich changes the outer diameter of the light intensity distribution.11. The system according to claim 10, wherein the light intensitydistribution comprises a multipole shape.
 12. The system according toclaim 11, further comprising an optical element which is arranged in anoptical path between the light source and the changers and whichconverts the light from the light source to a divergence light beam. 13.The system according to claim 12, wherein the optical element has atleast one of a diffractive and a refractive optical element.
 14. Thesystem according to claim 12, further comprising another optical elementwhich is interchangeable with the optical element and which converts thelight from the light source to a divergence light beam different fromthe divergence light beam created by the optical element.
 15. Anexposure apparatus comprising: the illumination system according toclaim 1; and a projection system for imaging a pattern onto a targetportion of a substrate.
 16. An exposure method comprising: illuminatinga pattern with the illumination system according to claim 1; andprojecting the illuminated pattern onto a target portion of a substrate.17. A method of transferring a pattern on an original onto a work,comprising the steps of: preparing said original; preparing said work;illuminating said original with the illumination optical system of claim1; and transferring said pattern onto said work.
 18. An illuminationoptical system for a projection imaging apparatus, comprising: a lightsource that emits illumination light; a light beam shape changingelement that diffuses incident light emitted by the light source in aplurality of directions; a zoom optical system that receives thediffused light; and an optical integrator that receives light from thezoom optical system in a modified illumination configuration having alight intensity distribution such that a lower light intensity is formedat a position near an optical axis relative to positions away from theoptical axis, and the optical integrator forms a secondary light sourcehaving a modified illumination configuration from the received light.19. The system of claim 18, wherein: the light beam shape changingelement comprises a plurality of interchangeable optical elements. 20.The system of claim 19, wherein: the light beam shape changing elementcomprises a plurality of interchangeable diffractive optical elementsthat each form a different modified illumination configuration incooperation with the zoom optical system at the optical integrator. 21.The system of claim 20, wherein: at least one diffractive opticalelement uses a phase difference of transmitted light to form a modifiedillumination configuration.
 22. The system of claim 18, wherein: thelight beam shape changing element forms a modified illuminationconfiguration on the optical integrator such that edges of illuminationregions are inclined with respect to a scanning direction of elementallenses in the optical integrator.
 23. The system of claim 18, wherein:the light beam shape changing element comprises at least one elementhoused within a protective housing.
 24. The system of claim 18, furthercomprising: a vibrator that vibrates at least one of the light beamshape changing element and an optical device positioned opticallybetween the light beam shape changing element and the opticalintegrator.
 25. The system of claim 18, further comprising: an annularratio variable optical system that receives light from the light beamshape changing element and transmits light to the zoom optical system,wherein the light beam shape changing element is a diffractive opticalelement that forms a ring shaped pattern in a far field, and opticalelements within the annular ratio variable optical system are adjustableto vary the annular ratio of an annular illumination pattern formed atthe optical integrator.
 26. The system of claim 25, wherein: the zoomoptical system is adjustable to vary a diameter of the annularillumination pattern formed at the optical integrator.
 27. The system ofclaim 25, wherein: the optical integrator is a wave front splitting typeoptical integrator.
 28. An illumination optical system for a projectionimaging apparatus, comprising: means for generating illumination light;means for diffusing the emitted light in a plurality of differentdirections; means for forming a plurality of light source images fromthe emitted light; and means for forming a secondary light source havinga modified illumination configuration from light that is diffused andused to form the plurality of light source images, the modifiedillumination configuration having a light intensity distribution suchthat a lower light intensity is formed at a position near an opticalaxis relative to positions away from the optical axis.